LeetCode OJ：Sudoku Solver（数独游戏）

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.

dfs,一直寻找，不行返回即可：

 class Solution {
 public:
     void solveSudoku(vector<vector<char>>& board) {
         doSudoku(board);
     }

     bool checkValid(vector<vector<char>>&board, int x, int y)
     {
         for(int i = ; i < ; i++){
             if(i!=x)
                 if(board[i][y] == board[x][y]) return false;
         }

         for(int j = ; j < ; j++){
             if(j != y)
                 if(board[x][j] == board[x][y]) return false;
         }

         for(int i = (x/) * ; i < (x/ + ) * ; ++i){
             for(int j = (y/) * ; j < (y/ + ) * ; ++j){
                 if((i!=x) || (j != y))
                     if(board[x][y] == board[i][j]) return false;
             }
         }
         return true;
     }

     bool doSudoku(vector<vector<char>> & board)
     {
         for(int row = ; row < ; ++row){
             for(int col = ; col < ; ++col){
                 if(board[row][col] == '.'){
                     for(int i = ; i <= ; ++i){
                         board[row][col] = '' + i;
                         if(checkValid(board, row, col)){
                             if(doSudoku(board)){
                                 return true;
                             }
                         }
                         board[row][col] = '.';
                     }
                     return false;
                 }
             }
         }
         return true;
     }
 };