[LeetCode][JavaScript]Sudoku Solver
Sudoku Solver
Write a program to solve a Sudoku puzzle by filling the empty cells.
Empty cells are indicated by the character ‘.‘
.
You may assume that there will be only one unique solution.
A sudoku puzzle...
...and its solution numbers marked in red.
又是一道DFS。
test case比较弱,只有6个,并且说好了都是可解的。
每到一格先看看是不是结束了或者不需要填,否则调用findCandidate方法找出在当前这一步所有可填的数字,然后开始递归。
每一轮递归回来都要把默认的‘.‘写回去,否则会影响下一轮的结果。
开了个flag记录是不是结束,如果已经遍历完就return掉,不用再找了。
1 /** 2 * @param {character[][]} board 3 * @return {void} Do not return anything, modify board in-place instead. 4 */ 5 var solveSudoku = function(board) { 6 var isComplete = false; 7 dfs(0, 0); 8 9 function dfs(x, y){ 10 if(isComplete){ 11 return; 12 } 13 var candidates = findCandidate(x, y); 14 if(x === 8 && y == 8){ 15 if(board[8][8] === ‘.‘){ 16 board[8][8] = candidates[0]; 17 } 18 isComplete = true; 19 return; 20 } 21 22 if(board[x][y] !== ‘.‘){ 23 if(y === 8){ 24 dfs(x + 1, 0); 25 return; 26 }else{ 27 dfs(x, y + 1); 28 return; 29 } 30 } 31 for(var i = 0; i < candidates.length; i++){ 32 board[x][y] = candidates[i]; 33 if(y === 8){ 34 dfs(x + 1, 0); 35 }else{ 36 dfs(x, y + 1); 37 } 38 if(!isComplete){ 39 board[x][y] = ‘.‘; 40 }else{ 41 return; 42 } 43 } 44 } 45 46 function findCandidate(x, y){ 47 var set = new Set(); 48 var candidate = []; 49 var cell = -1; 50 //row 51 for(i = 0; i < 9; i++){ 52 cell = board[x][i]; 53 if(!set.has(cell)){ 54 set.add(cell); 55 } 56 } 57 //column 58 for(i = 0; i < 9; i++){ 59 cell = board[i][y]; 60 if(!set.has(cell)){ 61 set.add(cell); 62 } 63 } 64 //square 65 var offsetX = parseInt(x / 3) * 3; 66 var offsetY = parseInt(y / 3) * 3; 67 for(i = 0; i <= 2; i++){ 68 for(j = 0; j <= 2; j++){ 69 cell = board[i + offsetX][j + offsetY]; 70 if(!set.has(cell)){ 71 set.add(cell); 72 } 73 } 74 } 75 //find candidate 76 for(i = 1; i <= 9; i++){ 77 if(!set.has(i + "")){ 78 candidate.push(i + ""); 79 } 80 } 81 return candidate; 82 } 83 };
附赠一个UT
1 function test(){ 2 var map = [ 3 [‘5‘,‘3‘,‘.‘,‘.‘,‘7‘,‘.‘,‘.‘,‘.‘,‘.‘], 4 [‘6‘,‘.‘,‘.‘,‘1‘,‘9‘,‘5‘,‘.‘,‘.‘,‘.‘], 5 [‘.‘,‘9‘,‘8‘,‘.‘,‘.‘,‘.‘,‘.‘,‘6‘,‘.‘], 6 [‘8‘,‘.‘,‘.‘,‘.‘,‘6‘,‘.‘,‘.‘,‘.‘,‘3‘], 7 [‘4‘,‘.‘,‘.‘,‘8‘,‘.‘,‘3‘,‘.‘,‘.‘,‘1‘], 8 [‘7‘,‘.‘,‘.‘,‘.‘,‘2‘,‘.‘,‘.‘,‘.‘,‘6‘], 9 [‘.‘,‘6‘,‘.‘,‘.‘,‘.‘,‘.‘,‘2‘,‘8‘,‘.‘], 10 [‘.‘,‘.‘,‘.‘,‘4‘,‘1‘,‘9‘,‘.‘,‘.‘,‘5‘], 11 [‘.‘,‘.‘,‘.‘,‘.‘,‘8‘,‘.‘,‘.‘,‘7‘,‘9‘] 12 ] 13 14 solveSudoku(map); 15 16 for(var m = 0; m < map.length; m++){ 17 var line = ""; 18 for(var n = 0; n < map[m].length; n++){ 19 line += (map[m][n] + ","); 20 } 21 console.log(line); 22 } 23 }
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