void solveSudoku(vector<vector<char>>& board) {

solve(board);

}

bool solve(vector<vector<char>>& board){

for(int i=0; i<board.size(); i++){

for(int j=0; j<board[0].size(); j++){

if(board[i][j] == '.'){

for(char c='1'; c<='9'; c++){

if(valid(c, board, i, j)){

board[i][j] = c;

if(solve(board) == true) return true;

else board[i][j]='.';

}

}

return false;

}

}

}

return true;

}

bool valid(char c, vector<vector<char>>& board, int row, int col){

for(int i=0; i<9; i++){

if(board[i][col] == c) return false;

if(board[row][i] == c) return false;

if(board[3*(row/3)+(i/3)][3*(col/3)+(i%3)] == c) return false;

}

return true;

}