编写一个程序，通过填充空格来解决数独问题。

数独的解法需 遵循如下规则：

数字 1-9 在每一行只能出现一次。
数字 1-9 在每一列只能出现一次。
数字 1-9 在每一个以粗实线分隔的 3x3 宫内只能出现一次。（请参考示例图）

数独部分空格内已填入了数字，空白格用 '.' 表示。

链接：https://leetcode-cn.com/problems/sudoku-solver

输入：board = [["5","3",".",".","7",".",".",".","."],["6",".",".","1","9","5",".",".","."],[".","9","8",".",".",".",".","6","."],["8",".",".",".","6",".",".",".","3"],["4",".",".","8",".","3",".",".","1"],["7",".",".",".","2",".",".",".","6"],[".","6",".",".",".",".","2","8","."],[".",".",".","4","1","9",".",".","5"],[".",".",".",".","8",".",".","7","9"]]
输出：[["5","3","4","6","7","8","9","1","2"],["6","7","2","1","9","5","3","4","8"],["1","9","8","3","4","2","5","6","7"],["8","5","9","7","6","1","4","2","3"],["4","2","6","8","5","3","7","9","1"],["7","1","3","9","2","4","8","5","6"],["9","6","1","5","3","7","2","8","4"],["2","8","7","4","1","9","6","3","5"],["3","4","5","2","8","6","1","7","9"]]
解释：输入的数独如上图所示，唯一有效的解决方案如下所示：

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/sudoku-solver

    public void solveSudoku(char[][] board) {
        dfs(board);
    }
    public boolean dfs(char[][] board)
    {
        for(int i=0;i<9;i++)
        {
            for(int j=0;j<9;j++)
            {
                if(board[i][j]=='.')
                {
                    for(int k=1;k<=9;k++)
                    {
                        if(smalldepend(i,j,board,(char)(k+'0'))) {
                            board[i][j] = (char) ('0' + k);
                            if(dfs(board))
                                return true;
                            board[i][j] = '.';
                        }
                    }
                    return false;
                }
            }
        }
        return true;
    }
    public boolean smalldepend(int x,int y,char[][] board,char data)
    {
        int startx=(int)(x/3)*3;
        int starty=(int)(y/3)*3;
        for(int i=startx;i<startx+3;i++)
        {
            for(int j=starty;j<starty+3;j++)
            {
                if(board[i][j]==data) return false;
            }
        }
        for(int i=0;i<9;i++)
        {
            if(board[x][i]==data)return false;
            if(board[i][y]==data)return false;
        }

        return true;
    }

    public static void main(String[] args) {
        char[][] board=new char[][]{
                {'5','3','.','.','7','.','.','.','.'},
                {'6','.','.','1','9','5','.','.','.'},
                {'.','9','8','.','.','.','.','6','.'},
                {'8','.','.','.','6','.','.','.','3'},
                {'4','.','.','8','.','3','.','.','1'},
                {'7','.','.','.','2','.','.','.','6'},
                {'.','6','.','.','.','.','2','8','.'},
                {'.','.','.','4','1','9','.','.','5'},
                {'.','.','.','.','8','.','.','7','9'}
        };
        new seqecStack().solveSudoku(board);
        for(int i=0;i<9;i++)
        {
            for(int j=0;j<9;j++)
            {
                System.out.print(board[i][j]);
            }
            System.out.println();
        }
    }