└── java


/java:
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 1 | class Solution {
 2 |     public void solveSudoku(char[][] board) {
 3 |         if(board == null || board.length == 0)
 4 |         return;
 5 |         solve(board);
 6 |     }
 7 |     public boolean solve(char[][] board){
 8 |         for(int i = 0; i < board.length; i++){
 9 |             for(int j = 0; j < board[0].length; j++){
10 |                 if(board[i][j] == '.'){
11 |                     for(char c = '1'; c <= '9'; c++){
12 |                         if(isValid(board, i, j, c)){
13 |                             board[i][j] = c;
14 |                             if(solve(board))
15 |                             return true;
16 |                             else
17 |                             board[i][j] = '.';
18 |                         }
19 |                     }
20 |                     return false;
21 |                 }
22 |             }
23 |         }
24 |         return true;
25 |     }
26 |     private boolean isValid(char[][] board, int row, int col, char c){
27 |         for(int i = 0; i < 9; i++) {
28 |             if(board[i][col] != '.' && board[i][col] == c) return false;
29 |             if(board[row][i] != '.' && board[row][i] == c) return false;
30 |             if(board[3 * (row / 3) + i / 3][3 * (col / 3) + i % 3] != '.' && board[3 * (row / 3) + i / 3][3 * (col / 3) + i % 3] == c) return false;
31 |         }
32 |         return true;
33 |     }
34 | }
35 | 


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