Sudoku Solver填数

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.

1. bool isValid(vector<vector<char> > &board, int a, int b) {  
2.         int i,j;  
3.         for(i = 0; i < 9; i++)  
4.             if(i != a && board[i][b] == board[a][b])  
5.                 return false;  
6.   
7.         for(j = 0; j < 9; j++)  
8.             if(j != b && board[a][j] == board[a][b])  
9.                 return false;  
10.   
11.         int x = a/3*3;  
12.         int y = b/3*3;  
13.         for(i = 0; i < 3; i++)  
14.             for(j = 0; j< 3; j++)  
15.                 if(x+i != a && y+j != b && board[x+i][y+j] == board[a][b])  
16.                     return false;  
17.         return true;  
18.     }  
19.     bool solveSudokudfs(vector<vector<char> > &board)  
20.     {  
21.         for(int i = 0; i < 9; i++)  
22.             for(int j = 0; j < 9; j++)  
23.             {  
24.                 if(board[i][j] == '.')  
25.                 {  
26.                     for(int k = 1; k <= 9; k++)  
27.                     {  
28.                         board[i][j] = '0' + k;  
29.                         if(isValid(board,i,j) && solveSudokudfs(board))  
30.                             return true;  
31.                         board[i][j] = '.';  
32.                     }  
33.                     return false;  
34.                 }  
35.             }  
36.         return true;  
37.     }  
38.     void solveSudoku(vector<vector<char> > &board) {  
39.         // Note: The Solution object is instantiated only once.  
40.         solveSudokudfs(board);  
41.     }