public static void  main(String[] args){
        char [][] board = new char[9][9];
        for(int i = 0; i < 9; ++i){
            Arrays.fill(board[i], '.');
        }
        board[0][0] = '9';
        new Sudoku_Solver().solveSudoku(board);
        for(int i = 0; i < 9; ++i){
            System.out.println(Arrays.toString(board[i]));
        }
    }