{ "id": "recursion-backtracking/backtracking", "version": 1, "deterministic": true, "url": "/dsa/recursion-backtracking/backtracking", "topic": { "slug": "recursion-backtracking", "title": "Recursion & Backtracking" }, "title": "Backtracking", "tagline": "Guess, explore, and when it dead-ends — put it back exactly as it was.", "vizKind": "grid", "complexity": { "time": { "best": "O(n!)", "average": "O(n!)", "worst": "O(n!)" }, "space": "O(n)", "growth": "quadratic", "note": "Factorial in the worst case — it is, after all, searching a huge space. But pruning is what makes it finish at all: the moment a partial board is impossible, every arrangement built on it is discarded at once. The space is just the recursion depth, O(n)." }, "code": { "javascript": "// Place N queens so none can attack another.\nfunction solve(board, row, n) {\n if (row === n) return true; // all placed — done\n\n for (let col = 0; col < n; col++) {\n if (!isSafe(board, row, col, n)) continue;\n\n board[row] = col; // choose\n if (solve(board, row + 1, n)) return true; // explore\n board[row] = -1; // un-choose — BACKTRACK\n }\n\n return false; // no column worked in this row\n}\n\nfunction isSafe(board, row, col, n) {\n for (let r = 0; r < row; r++) {\n const c = board[r];\n if (c === col) return false; // same column\n if (Math.abs(c - col) === row - r) return false; // same diagonal\n }\n return true;\n}", "python": "# Place N queens so none can attack another.\ndef solve(board, row, n):\n if row == n: return True # all placed — done\n\n for col in range(n):\n if not is_safe(board, row, col): continue\n\n board[row] = col # choose\n if solve(board, row + 1, n): return True # explore\n board[row] = -1 # un-choose — BACKTRACK\n\n return False # no column worked in this row\n\n\ndef is_safe(board, row, col):\n for r in range(row):\n c = board[r]\n if c == col: return False # same column\n if abs(c - col) == row - r: return False # same diagonal\n return True\n", "java": "// Place N queens so none can attack another.\nboolean solve(int[] board, int row, int n) {\n if (row == n) return true; // all placed — done\n\n for (int col = 0; col < n; col++) {\n if (!isSafe(board, row, col)) continue;\n\n board[row] = col; // choose\n if (solve(board, row + 1, n)) return true; // explore\n board[row] = -1; // un-choose — BACKTRACK\n }\n\n return false; // no column worked in this row\n}\n\nboolean isSafe(int[] board, int row, int col) {\n for (int r = 0; r < row; r++) {\n int c = board[r];\n if (c == col) return false; // same column\n if (Math.abs(c - col) == row - r) return false; // same diagonal\n }\n return true;\n}", "cpp": "// Place N queens so none can attack another.\nbool solve(vector& board, int row, int n) {\n if (row == n) return true; // all placed — done\n\n for (int col = 0; col < n; col++) {\n if (!isSafe(board, row, col)) continue;\n\n board[row] = col; // choose\n if (solve(board, row + 1, n)) return true; // explore\n board[row] = -1; // un-choose — BACKTRACK\n }\n\n return false; // no column worked in this row\n}\n\nbool isSafe(vector& board, int row, int col) {\n for (int r = 0; r < row; r++) {\n int c = board[r];\n if (c == col) return false; // same column\n if (abs(c - col) == row - r) return false; // same diagonal\n }\n return true;\n}" }, "defaultInput": [ 6 ], "defaultTarget": null, "inputHint": "Board size 4 to 7. Watch queens get placed — and lifted back off.", "pitfalls": [ { "wrong": "Forgetting to un-choose.", "right": "The single most common bug. If you don't restore the state on the way back up, the next branch starts from a dirty board and the answers are nonsense." }, { "wrong": "Checking validity only at the end.", "right": "That's brute force, and it's astronomically slower. Check as you go, so an impossible partial answer is abandoned before you waste time extending it." }, { "wrong": "Mutating shared state and not copying the result when you find it.", "right": "The board keeps changing as you backtrack. If you store a reference to it, you'll come back later and find your 'answer' has been unwound. Copy it out." }, { "wrong": "Thinking backtracking is a different algorithm for each puzzle.", "right": "It isn't. Subsets, permutations, sudoku, N-Queens, word search — all the same choose/explore/un-choose skeleton. Learn the shape once." } ], "quiz": [ { "q": "What are the three moves of backtracking?", "options": [ "Sort, search, return", "Choose, explore, un-choose", "Split, solve, merge", "Push, pop, peek" ], "answer": 1, "why": "Choose an option, explore what follows, and if it fails, un-choose it — restoring the state exactly. That third move is what the technique is named after." }, { "q": "What makes backtracking usable instead of hopeless?", "options": [ "Recursion", "Pruning — abandoning a whole branch the moment a partial answer is proved impossible", "Sorting the input first", "Using a stack" ], "answer": 1, "why": "Brute force checks only complete arrangements. Backtracking checks as it goes, so one impossible partial board throws away every arrangement that would have started that way." }, { "q": "You forget to un-choose after a failed branch. What happens?", "options": [ "It runs faster", "The next branch starts from a dirty state, and the answers are wrong", "Nothing — it's optional", "It crashes immediately" ], "answer": 1, "why": "The leftover queen is still on the board when you try the next column, so every subsequent decision is made against a corrupted state. It usually doesn't crash — it just quietly lies." } ], "problems": [ { "name": "Subsets", "difficulty": "Medium", "url": "https://leetcode.com/problems/subsets/" }, { "name": "Permutations", "difficulty": "Medium", "url": "https://leetcode.com/problems/permutations/" }, { "name": "Combination Sum", "difficulty": "Medium", "url": "https://leetcode.com/problems/combination-sum/" }, { "name": "N-Queens", "difficulty": "Hard", "url": "https://leetcode.com/problems/n-queens/" }, { "name": "Word Search", "difficulty": "Medium", "url": "https://leetcode.com/problems/word-search/" } ], "trace": { "note": "Each frame is one immutable step: data snapshot, pointers, per-index roles, executing code line, and a one-sentence explanation.", "length": 255, "frames": [ { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "6 queens · none may attack another" }, "pointers": [], "highlights": [], "codeLine": 2, "variables": { "n": 6, "placed": 0 }, "explanation": "Place 6 queens on a 6×6 board so no two share a row, a column, or a diagonal. One queen per row — the only question is which column.", "stats": { "comparisons": 0, "swaps": 0 }, "accent": "active" }, { "data": { "cells": [ [ { "value": "?", "role": "active", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 0 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 0, "col": 0, "safe": true, "placed": 0 }, "explanation": "Row 0, column 0: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 1, "swaps": 0 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 0" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 0, "col": 0, "placed": 1 }, "explanation": "Place a queen at (0, 0) and move on to row 1. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 1, "swaps": 1 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 0, "safe": false, "placed": 1 }, "explanation": "Row 1, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 2, "swaps": 1 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 1, "safe": false, "placed": 1 }, "explanation": "Row 1, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 3, "swaps": 1 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 2, "safe": true, "placed": 1 }, "explanation": "Row 1, column 2: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 4, "swaps": 1 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 1" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 1, "col": 2, "placed": 2 }, "explanation": "Place a queen at (1, 2) and move on to row 2. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 4, "swaps": 2 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 0, "safe": false, "placed": 2 }, "explanation": "Row 2, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 5, "swaps": 2 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 1, "safe": false, "placed": 2 }, "explanation": "Row 2, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 6, "swaps": 2 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 2, "safe": false, "placed": 2 }, "explanation": "Row 2, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 7, "swaps": 2 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 3, "safe": false, "placed": 2 }, "explanation": "Row 2, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 8, "swaps": 2 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 4, "safe": true, "placed": 2 }, "explanation": "Row 2, column 4: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 9, "swaps": 2 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 4, "placed": 3 }, "explanation": "Place a queen at (2, 4) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 9, "swaps": 3 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": false, "placed": 3 }, "explanation": "Row 3, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 10, "swaps": 3 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 1, "safe": true, "placed": 3 }, "explanation": "Row 3, column 1: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 11, "swaps": 3 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 1, "placed": 4 }, "explanation": "Place a queen at (3, 1) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 11, "swaps": 4 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 12, "swaps": 4 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 13, "swaps": 4 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": false, "placed": 4 }, "explanation": "Row 4, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 14, "swaps": 4 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 3, "safe": true, "placed": 4 }, "explanation": "Row 4, column 3: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 15, "swaps": 4 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 4" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 4, "col": 3, "placed": 5 }, "explanation": "Place a queen at (4, 3) and move on to row 5. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 15, "swaps": 5 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 0, "safe": false, "placed": 5 }, "explanation": "Row 5, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 16, "swaps": 5 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 1, "safe": false, "placed": 5 }, "explanation": "Row 5, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 17, "swaps": 5 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 2, "safe": false, "placed": 5 }, "explanation": "Row 5, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 18, "swaps": 5 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 3, "safe": false, "placed": 5 }, "explanation": "Row 5, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 19, "swaps": 5 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 4, "safe": false, "placed": 5 }, "explanation": "Row 5, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 20, "swaps": 5 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 5, "safe": false, "placed": 5 }, "explanation": "Row 5, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 21, "swaps": 5 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 5 }, "explanation": "Every column in row 5 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 21, "swaps": 5 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 4, "col": 3, "placed": 4 }, "explanation": "Row 5 had nowhere to go, so the guess at (4, 3) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 21, "swaps": 6 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 4, "safe": false, "placed": 4 }, "explanation": "Row 4, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 22, "swaps": 6 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 5, "safe": false, "placed": 4 }, "explanation": "Row 4, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 23, "swaps": 6 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 4 }, "explanation": "Every column in row 4 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 23, "swaps": 6 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 3, "col": 1, "placed": 3 }, "explanation": "Row 4 had nowhere to go, so the guess at (3, 1) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 23, "swaps": 7 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 2, "safe": false, "placed": 3 }, "explanation": "Row 3, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 24, "swaps": 7 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 3, "safe": false, "placed": 3 }, "explanation": "Row 3, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 25, "swaps": 7 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 4, "safe": false, "placed": 3 }, "explanation": "Row 3, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 26, "swaps": 7 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 5, "safe": false, "placed": 3 }, "explanation": "Row 3, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 27, "swaps": 7 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 3 }, "explanation": "Every column in row 3 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 27, "swaps": 7 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 2, "col": 4, "placed": 2 }, "explanation": "Row 3 had nowhere to go, so the guess at (2, 4) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 27, "swaps": 8 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "active", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 5, "safe": true, "placed": 2 }, "explanation": "Row 2, column 5: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 28, "swaps": 8 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 5, "placed": 3 }, "explanation": "Place a queen at (2, 5) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 28, "swaps": 9 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": false, "placed": 3 }, "explanation": "Row 3, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 29, "swaps": 9 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 1, "safe": true, "placed": 3 }, "explanation": "Row 3, column 1: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 30, "swaps": 9 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 1, "placed": 4 }, "explanation": "Place a queen at (3, 1) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 30, "swaps": 10 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 31, "swaps": 10 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 32, "swaps": 10 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": false, "placed": 4 }, "explanation": "Row 4, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 33, "swaps": 10 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 3, "safe": false, "placed": 4 }, "explanation": "Row 4, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 34, "swaps": 10 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 4, "safe": false, "placed": 4 }, "explanation": "Row 4, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 35, "swaps": 10 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 5, "safe": false, "placed": 4 }, "explanation": "Row 4, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 36, "swaps": 10 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 4 }, "explanation": "Every column in row 4 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 36, "swaps": 10 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 3, "col": 1, "placed": 3 }, "explanation": "Row 4 had nowhere to go, so the guess at (3, 1) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 36, "swaps": 11 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 2, "safe": false, "placed": 3 }, "explanation": "Row 3, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 37, "swaps": 11 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 3, "safe": false, "placed": 3 }, "explanation": "Row 3, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 38, "swaps": 11 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 4, "safe": false, "placed": 3 }, "explanation": "Row 3, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 39, "swaps": 11 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 5, "safe": false, "placed": 3 }, "explanation": "Row 3, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 40, "swaps": 11 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 3 }, "explanation": "Every column in row 3 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 40, "swaps": 11 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 2, "col": 5, "placed": 2 }, "explanation": "Row 3 had nowhere to go, so the guess at (2, 5) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 40, "swaps": 12 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 2 }, "explanation": "Every column in row 2 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 40, "swaps": 12 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 1, "col": 2, "placed": 1 }, "explanation": "Row 2 had nowhere to go, so the guess at (1, 2) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 40, "swaps": 13 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 3, "safe": true, "placed": 1 }, "explanation": "Row 1, column 3: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 41, "swaps": 13 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 1" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 1, "col": 3, "placed": 2 }, "explanation": "Place a queen at (1, 3) and move on to row 2. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 41, "swaps": 14 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 0, "safe": false, "placed": 2 }, "explanation": "Row 2, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 42, "swaps": 14 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 1, "safe": true, "placed": 2 }, "explanation": "Row 2, column 1: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 43, "swaps": 14 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 1, "placed": 3 }, "explanation": "Place a queen at (2, 1) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 43, "swaps": 15 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": false, "placed": 3 }, "explanation": "Row 3, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 44, "swaps": 15 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 1, "safe": false, "placed": 3 }, "explanation": "Row 3, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 45, "swaps": 15 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 2, "safe": false, "placed": 3 }, "explanation": "Row 3, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 46, "swaps": 15 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 3, "safe": false, "placed": 3 }, "explanation": "Row 3, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 47, "swaps": 15 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 4, "safe": true, "placed": 3 }, "explanation": "Row 3, column 4: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 48, "swaps": 15 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 4, "placed": 4 }, "explanation": "Place a queen at (3, 4) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 48, "swaps": 16 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 49, "swaps": 16 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 50, "swaps": 16 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": true, "placed": 4 }, "explanation": "Row 4, column 2: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 51, "swaps": 16 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 4" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 4, "col": 2, "placed": 5 }, "explanation": "Place a queen at (4, 2) and move on to row 5. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 51, "swaps": 17 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 0, "safe": false, "placed": 5 }, "explanation": "Row 5, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 52, "swaps": 17 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 1, "safe": false, "placed": 5 }, "explanation": "Row 5, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 53, "swaps": 17 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 2, "safe": false, "placed": 5 }, "explanation": "Row 5, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 54, "swaps": 17 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 3, "safe": false, "placed": 5 }, "explanation": "Row 5, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 55, "swaps": 17 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 4, "safe": false, "placed": 5 }, "explanation": "Row 5, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 56, "swaps": 17 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 5, "safe": false, "placed": 5 }, "explanation": "Row 5, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 57, "swaps": 17 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 5 }, "explanation": "Every column in row 5 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 57, "swaps": 17 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 4, "col": 2, "placed": 4 }, "explanation": "Row 5 had nowhere to go, so the guess at (4, 2) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 57, "swaps": 18 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 3, "safe": false, "placed": 4 }, "explanation": "Row 4, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 58, "swaps": 18 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 4, "safe": false, "placed": 4 }, "explanation": "Row 4, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 59, "swaps": 18 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 5, "safe": false, "placed": 4 }, "explanation": "Row 4, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 60, "swaps": 18 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 4 }, "explanation": "Every column in row 4 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 60, "swaps": 18 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 3, "col": 4, "placed": 3 }, "explanation": "Row 4 had nowhere to go, so the guess at (3, 4) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 60, "swaps": 19 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 5, "safe": false, "placed": 3 }, "explanation": "Row 3, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 61, "swaps": 19 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 3 }, "explanation": "Every column in row 3 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 61, "swaps": 19 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 2, "col": 1, "placed": 2 }, "explanation": "Row 3 had nowhere to go, so the guess at (2, 1) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 61, "swaps": 20 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 2, "safe": false, "placed": 2 }, "explanation": "Row 2, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 62, "swaps": 20 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 3, "safe": false, "placed": 2 }, "explanation": "Row 2, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 63, "swaps": 20 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 4, "safe": false, "placed": 2 }, "explanation": "Row 2, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 64, "swaps": 20 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 5, "safe": true, "placed": 2 }, "explanation": "Row 2, column 5: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 65, "swaps": 20 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 5, "placed": 3 }, "explanation": "Place a queen at (2, 5) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 65, "swaps": 21 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": false, "placed": 3 }, "explanation": "Row 3, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 66, "swaps": 21 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 1, "safe": false, "placed": 3 }, "explanation": "Row 3, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 67, "swaps": 21 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 2, "safe": true, "placed": 3 }, "explanation": "Row 3, column 2: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 68, "swaps": 21 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 2, "placed": 4 }, "explanation": "Place a queen at (3, 2) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 68, "swaps": 22 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 69, "swaps": 22 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 70, "swaps": 22 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": false, "placed": 4 }, "explanation": "Row 4, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 71, "swaps": 22 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 3, "safe": false, "placed": 4 }, "explanation": "Row 4, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 72, "swaps": 22 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 4, "safe": false, "placed": 4 }, "explanation": "Row 4, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 73, "swaps": 22 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 5, "safe": false, "placed": 4 }, "explanation": "Row 4, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 74, "swaps": 22 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 4 }, "explanation": "Every column in row 4 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 74, "swaps": 22 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 3, "col": 2, "placed": 3 }, "explanation": "Row 4 had nowhere to go, so the guess at (3, 2) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 74, "swaps": 23 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 3, "safe": false, "placed": 3 }, "explanation": "Row 3, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 75, "swaps": 23 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 4, "safe": false, "placed": 3 }, "explanation": "Row 3, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 76, "swaps": 23 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 5, "safe": false, "placed": 3 }, "explanation": "Row 3, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 77, "swaps": 23 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 3 }, "explanation": "Every column in row 3 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 77, "swaps": 23 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 2, "col": 5, "placed": 2 }, "explanation": "Row 3 had nowhere to go, so the guess at (2, 5) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 77, "swaps": 24 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 2 }, "explanation": "Every column in row 2 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 77, "swaps": 24 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 1, "col": 3, "placed": 1 }, "explanation": "Row 2 had nowhere to go, so the guess at (1, 3) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 77, "swaps": 25 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 4, "safe": true, "placed": 1 }, "explanation": "Row 1, column 4: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 78, "swaps": 25 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 1" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 1, "col": 4, "placed": 2 }, "explanation": "Place a queen at (1, 4) and move on to row 2. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 78, "swaps": 26 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 0, "safe": false, "placed": 2 }, "explanation": "Row 2, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 79, "swaps": 26 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 1, "safe": true, "placed": 2 }, "explanation": "Row 2, column 1: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 80, "swaps": 26 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 1, "placed": 3 }, "explanation": "Place a queen at (2, 1) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 80, "swaps": 27 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": false, "placed": 3 }, "explanation": "Row 3, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 81, "swaps": 27 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 1, "safe": false, "placed": 3 }, "explanation": "Row 3, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 82, "swaps": 27 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 2, "safe": false, "placed": 3 }, "explanation": "Row 3, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 83, "swaps": 27 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 3, "safe": false, "placed": 3 }, "explanation": "Row 3, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 84, "swaps": 27 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 4, "safe": false, "placed": 3 }, "explanation": "Row 3, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 85, "swaps": 27 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 5, "safe": true, "placed": 3 }, "explanation": "Row 3, column 5: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 86, "swaps": 27 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 5, "placed": 4 }, "explanation": "Place a queen at (3, 5) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 86, "swaps": 28 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 87, "swaps": 28 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 88, "swaps": 28 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": true, "placed": 4 }, "explanation": "Row 4, column 2: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 89, "swaps": 28 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 4" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 4, "col": 2, "placed": 5 }, "explanation": "Place a queen at (4, 2) and move on to row 5. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 89, "swaps": 29 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 0, "safe": false, "placed": 5 }, "explanation": "Row 5, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 90, "swaps": 29 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 1, "safe": false, "placed": 5 }, "explanation": "Row 5, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 91, "swaps": 29 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 2, "safe": false, "placed": 5 }, "explanation": "Row 5, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 92, "swaps": 29 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 3, "safe": false, "placed": 5 }, "explanation": "Row 5, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 93, "swaps": 29 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 4, "safe": false, "placed": 5 }, "explanation": "Row 5, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 94, "swaps": 29 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 5, "safe": false, "placed": 5 }, "explanation": "Row 5, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 95, "swaps": 29 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 5 }, "explanation": "Every column in row 5 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 95, "swaps": 29 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 4, "col": 2, "placed": 4 }, "explanation": "Row 5 had nowhere to go, so the guess at (4, 2) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 95, "swaps": 30 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 3, "safe": false, "placed": 4 }, "explanation": "Row 4, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 96, "swaps": 30 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 4, "safe": false, "placed": 4 }, "explanation": "Row 4, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 97, "swaps": 30 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 5, "safe": false, "placed": 4 }, "explanation": "Row 4, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 98, "swaps": 30 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 4 }, "explanation": "Every column in row 4 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 98, "swaps": 30 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 3, "col": 5, "placed": 3 }, "explanation": "Row 4 had nowhere to go, so the guess at (3, 5) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 98, "swaps": 31 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 3 }, "explanation": "Every column in row 3 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 98, "swaps": 31 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 2, "col": 1, "placed": 2 }, "explanation": "Row 3 had nowhere to go, so the guess at (2, 1) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 98, "swaps": 32 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 2, "safe": false, "placed": 2 }, "explanation": "Row 2, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 99, "swaps": 32 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 3, "safe": false, "placed": 2 }, "explanation": "Row 2, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 100, "swaps": 32 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 4, "safe": false, "placed": 2 }, "explanation": "Row 2, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 101, "swaps": 32 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 5, "safe": false, "placed": 2 }, "explanation": "Row 2, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 102, "swaps": 32 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 2 }, "explanation": "Every column in row 2 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 102, "swaps": 32 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 1, "col": 4, "placed": 1 }, "explanation": "Row 2 had nowhere to go, so the guess at (1, 4) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 102, "swaps": 33 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "?", "role": "active", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 5, "safe": true, "placed": 1 }, "explanation": "Row 1, column 5: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 103, "swaps": 33 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 1" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 1, "col": 5, "placed": 2 }, "explanation": "Place a queen at (1, 5) and move on to row 2. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 103, "swaps": 34 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 0, "safe": false, "placed": 2 }, "explanation": "Row 2, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 104, "swaps": 34 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 1, "safe": true, "placed": 2 }, "explanation": "Row 2, column 1: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 105, "swaps": 34 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 1, "placed": 3 }, "explanation": "Place a queen at (2, 1) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 105, "swaps": 35 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": false, "placed": 3 }, "explanation": "Row 3, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 106, "swaps": 35 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 1, "safe": false, "placed": 3 }, "explanation": "Row 3, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 107, "swaps": 35 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 2, "safe": false, "placed": 3 }, "explanation": "Row 3, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 108, "swaps": 35 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 3, "safe": false, "placed": 3 }, "explanation": "Row 3, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 109, "swaps": 35 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 4, "safe": true, "placed": 3 }, "explanation": "Row 3, column 4: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 110, "swaps": 35 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 4, "placed": 4 }, "explanation": "Place a queen at (3, 4) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 110, "swaps": 36 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 111, "swaps": 36 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 112, "swaps": 36 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": false, "placed": 4 }, "explanation": "Row 4, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 113, "swaps": 36 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 3, "safe": false, "placed": 4 }, "explanation": "Row 4, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 114, "swaps": 36 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 4, "safe": false, "placed": 4 }, "explanation": "Row 4, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 115, "swaps": 36 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 5, "safe": false, "placed": 4 }, "explanation": "Row 4, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 116, "swaps": 36 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 4 }, "explanation": "Every column in row 4 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 116, "swaps": 36 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 3, "col": 4, "placed": 3 }, "explanation": "Row 4 had nowhere to go, so the guess at (3, 4) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 116, "swaps": 37 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 5, "safe": false, "placed": 3 }, "explanation": "Row 3, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 117, "swaps": 37 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 3 }, "explanation": "Every column in row 3 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 117, "swaps": 37 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 2, "col": 1, "placed": 2 }, "explanation": "Row 3 had nowhere to go, so the guess at (2, 1) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 117, "swaps": 38 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 2, "safe": false, "placed": 2 }, "explanation": "Row 2, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 118, "swaps": 38 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 3, "safe": true, "placed": 2 }, "explanation": "Row 2, column 3: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 119, "swaps": 38 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 3, "placed": 3 }, "explanation": "Place a queen at (2, 3) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 119, "swaps": 39 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": false, "placed": 3 }, "explanation": "Row 3, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 120, "swaps": 39 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 1, "safe": true, "placed": 3 }, "explanation": "Row 3, column 1: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 121, "swaps": 39 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 1, "placed": 4 }, "explanation": "Place a queen at (3, 1) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 121, "swaps": 40 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 122, "swaps": 40 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 123, "swaps": 40 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": false, "placed": 4 }, "explanation": "Row 4, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 124, "swaps": 40 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 3, "safe": false, "placed": 4 }, "explanation": "Row 4, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 125, "swaps": 40 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 4, "safe": false, "placed": 4 }, "explanation": "Row 4, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 126, "swaps": 40 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 5, "safe": false, "placed": 4 }, "explanation": "Row 4, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 127, "swaps": 40 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 4 }, "explanation": "Every column in row 4 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 127, "swaps": 40 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 3, "col": 1, "placed": 3 }, "explanation": "Row 4 had nowhere to go, so the guess at (3, 1) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 127, "swaps": 41 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 2, "safe": false, "placed": 3 }, "explanation": "Row 3, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 128, "swaps": 41 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 3, "safe": false, "placed": 3 }, "explanation": "Row 3, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 129, "swaps": 41 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 4, "safe": false, "placed": 3 }, "explanation": "Row 3, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 130, "swaps": 41 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 5, "safe": false, "placed": 3 }, "explanation": "Row 3, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 131, "swaps": 41 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 3 }, "explanation": "Every column in row 3 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 131, "swaps": 41 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 2, "col": 3, "placed": 2 }, "explanation": "Row 3 had nowhere to go, so the guess at (2, 3) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 131, "swaps": 42 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 4, "safe": false, "placed": 2 }, "explanation": "Row 2, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 132, "swaps": 42 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 5, "safe": false, "placed": 2 }, "explanation": "Row 2, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 133, "swaps": 42 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 2 }, "explanation": "Every column in row 2 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 133, "swaps": 42 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 1, "col": 5, "placed": 1 }, "explanation": "Row 2 had nowhere to go, so the guess at (1, 5) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 133, "swaps": 43 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 1 }, "explanation": "Every column in row 1 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 133, "swaps": 43 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 0, "col": 0, "placed": 0 }, "explanation": "Row 1 had nowhere to go, so the guess at (0, 0) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 133, "swaps": 44 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 0 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 0, "col": 1, "safe": true, "placed": 0 }, "explanation": "Row 0, column 1: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 134, "swaps": 44 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 0" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 0, "col": 1, "placed": 1 }, "explanation": "Place a queen at (0, 1) and move on to row 1. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 134, "swaps": 45 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 0, "safe": false, "placed": 1 }, "explanation": "Row 1, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 135, "swaps": 45 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 1, "safe": false, "placed": 1 }, "explanation": "Row 1, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 136, "swaps": 45 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 2, "safe": false, "placed": 1 }, "explanation": "Row 1, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 137, "swaps": 45 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 1 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 1, "col": 3, "safe": true, "placed": 1 }, "explanation": "Row 1, column 3: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 138, "swaps": 45 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 1" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 1, "col": 3, "placed": 2 }, "explanation": "Place a queen at (1, 3) and move on to row 2. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 138, "swaps": 46 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 0, "safe": true, "placed": 2 }, "explanation": "Row 2, column 0: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 139, "swaps": 46 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 0, "placed": 3 }, "explanation": "Place a queen at (2, 0) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 139, "swaps": 47 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": false, "placed": 3 }, "explanation": "Row 3, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 140, "swaps": 47 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 1, "safe": false, "placed": 3 }, "explanation": "Row 3, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 141, "swaps": 47 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 2, "safe": true, "placed": 3 }, "explanation": "Row 3, column 2: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 142, "swaps": 47 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 2, "placed": 4 }, "explanation": "Place a queen at (3, 2) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 142, "swaps": 48 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 143, "swaps": 48 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 144, "swaps": 48 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": false, "placed": 4 }, "explanation": "Row 4, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 145, "swaps": 48 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 3, "safe": false, "placed": 4 }, "explanation": "Row 4, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 146, "swaps": 48 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 4, "safe": true, "placed": 4 }, "explanation": "Row 4, column 4: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 147, "swaps": 48 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 4" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 4, "col": 4, "placed": 5 }, "explanation": "Place a queen at (4, 4) and move on to row 5. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 147, "swaps": 49 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 0, "safe": false, "placed": 5 }, "explanation": "Row 5, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 148, "swaps": 49 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 1, "safe": false, "placed": 5 }, "explanation": "Row 5, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 149, "swaps": 49 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 2, "safe": false, "placed": 5 }, "explanation": "Row 5, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 150, "swaps": 49 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 3, "safe": false, "placed": 5 }, "explanation": "Row 5, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 151, "swaps": 49 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 4, "safe": false, "placed": 5 }, "explanation": "Row 5, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 152, "swaps": 49 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 5, "safe": false, "placed": 5 }, "explanation": "Row 5, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 153, "swaps": 49 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 5 }, "explanation": "Every column in row 5 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 153, "swaps": 49 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 4, "col": 4, "placed": 4 }, "explanation": "Row 5 had nowhere to go, so the guess at (4, 4) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 153, "swaps": 50 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 5, "safe": false, "placed": 4 }, "explanation": "Row 4, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 154, "swaps": 50 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 4 }, "explanation": "Every column in row 4 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 154, "swaps": 50 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 3, "col": 2, "placed": 3 }, "explanation": "Row 4 had nowhere to go, so the guess at (3, 2) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 154, "swaps": 51 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 3, "safe": false, "placed": 3 }, "explanation": "Row 3, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 155, "swaps": 51 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 4, "safe": false, "placed": 3 }, "explanation": "Row 3, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 156, "swaps": 51 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 5, "safe": false, "placed": 3 }, "explanation": "Row 3, column 5: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 157, "swaps": 51 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 has no safe column" }, "pointers": [], "highlights": [], "codeLine": 14, "variables": { "row": 3 }, "explanation": "Every column in row 3 is attacked. There's nothing to try here — hand the failure back up, so whoever guessed before us can change their mind.", "stats": { "comparisons": 157, "swaps": 51 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "?", "role": "discarded", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "dead end — lifting the queen back off" }, "pointers": [], "highlights": [], "codeLine": 10, "variables": { "row": 2, "col": 0, "placed": 2 }, "explanation": "Row 3 had nowhere to go, so the guess at (2, 0) was wrong. Lift the queen back off and try the next column. *This* is backtracking — undoing a choice, exactly.", "stats": { "comparisons": 157, "swaps": 52 }, "accent": "swap" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 1, "safe": false, "placed": 2 }, "explanation": "Row 2, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 158, "swaps": 52 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 2, "safe": false, "placed": 2 }, "explanation": "Row 2, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 159, "swaps": 52 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 3, "safe": false, "placed": 2 }, "explanation": "Row 2, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 160, "swaps": 52 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 4, "safe": false, "placed": 2 }, "explanation": "Row 2, column 4: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 161, "swaps": 52 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": false } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 2 · trying column 5" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 2, "col": 5, "safe": true, "placed": 2 }, "explanation": "Row 2, column 5: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 162, "swaps": 52 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 2" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 2, "col": 5, "placed": 3 }, "explanation": "Place a queen at (2, 5) and move on to row 3. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 162, "swaps": 53 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 3 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 3, "col": 0, "safe": true, "placed": 3 }, "explanation": "Row 3, column 0: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 163, "swaps": 53 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 3" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 3, "col": 0, "placed": 4 }, "explanation": "Place a queen at (3, 0) and move on to row 4. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 163, "swaps": 54 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 0, "safe": false, "placed": 4 }, "explanation": "Row 4, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 164, "swaps": 54 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 1, "safe": false, "placed": 4 }, "explanation": "Row 4, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 165, "swaps": 54 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 4 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 4, "col": 2, "safe": true, "placed": 4 }, "explanation": "Row 4, column 2: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 166, "swaps": 54 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 4" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 4, "col": 2, "placed": 5 }, "explanation": "Place a queen at (4, 2) and move on to row 5. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 166, "swaps": 55 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 0" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 0, "safe": false, "placed": 5 }, "explanation": "Row 5, column 0: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 167, "swaps": 55 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 1" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 1, "safe": false, "placed": 5 }, "explanation": "Row 5, column 1: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 168, "swaps": 55 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 2" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 2, "safe": false, "placed": 5 }, "explanation": "Row 5, column 2: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 169, "swaps": 55 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "discarded", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 3" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 3, "safe": false, "placed": 5 }, "explanation": "Row 5, column 3: a queen above already covers this square. Can't go here.", "stats": { "comparisons": 170, "swaps": 55 }, "accent": "discarded" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "?", "role": "active", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "row 5 · trying column 4" }, "pointers": [], "highlights": [], "codeLine": 6, "variables": { "row": 5, "col": 4, "safe": true, "placed": 5 }, "explanation": "Row 5, column 4: no queen above attacks this square. It's safe — try it.", "stats": { "comparisons": 171, "swaps": 55 }, "accent": "compare" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "queen placed at row 5" }, "pointers": [], "highlights": [], "codeLine": 8, "variables": { "row": 5, "col": 4, "placed": 6 }, "explanation": "Place a queen at (5, 4) and move on to row 6. This is a guess — we don't know yet whether it leads anywhere.", "stats": { "comparisons": 171, "swaps": 56 }, "accent": "sorted" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "solved" }, "pointers": [], "highlights": [], "codeLine": 3, "variables": { "placed": 6 }, "explanation": "All 6 queens are placed, and not one can attack another. Solved.", "stats": { "comparisons": 171, "swaps": 56 }, "accent": "found" }, { "data": { "cells": [ [ { "value": "", "source": false }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": false }, { "value": "", "source": false } ], [ { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false } ], [ { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true }, { "value": "", "source": false }, { "value": "", "source": true } ], [ { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "", "source": true }, { "value": "♛", "role": "sorted", "source": false }, { "value": "", "source": true } ] ], "rowLabels": [ "0", "1", "2", "3", "4", "5" ], "colLabels": [ "0", "1", "2", "3", "4", "5" ], "caption": "solved · 56 placements and removals" }, "pointers": [], "highlights": [], "codeLine": 3, "variables": { "queens": 6, "squaresTested": 171, "placesAndUndos": 56 }, "explanation": "Done. It took 171 square-checks and 56 placements-and-removals. Brute force would have tried every arrangement; backtracking abandons a whole branch the moment it proves impossible — that pruning is what makes it usable.", "stats": { "comparisons": 171, "swaps": 56 }, "accent": "found" } ] } }