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;

     }

 };