public void solveSudoku(char[][] board){

if(board == null || board.length == 0){

return;

}

solve(board);

}

private boolean solve(char[][] board) {

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

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

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

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

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

board[i][j] = c;

if (solve(board)) return true;

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

}

}

return false;

}

}

}

return true;

}

private boolean isValid(char[][] board,int row,int col,char c){

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

if (board[i][col] != '.' && board[i][col] == c) return false;

if (board[row][i] != '.' && board[row][i] == c) return false;

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;

}

return true;

}