leetcode 37. 解数独

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。

 

示例：

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：

 

提示：

board.length == 9
board[i].length == 9
board[i][j] 是一位数字或者 '.'
题目数据 保证 输入数独仅有一个解

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/sudoku-solver
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

 

class Solution {
     public void solveSudoku(char[][] matrix) {
        bb(matrix, 0, 0);
      
    }
    public boolean bb(char[][] matrix, int x, int y) {

        if (x == 8 && y == 9) {
            return true;
        }

        if (y == 9) {
            y = 0;
            x++;
        }

        if (matrix[x][y] != '.') {
            return bb(matrix, x, y + 1);
        }

        boolean flag = false;
        List<Character> cc = cc(matrix, x, y);

        if (cc.size() == 0) {
            return flag;
        }
        for (Character cter : cc) {
            matrix[x][y] = cter;
            if (bb(matrix, x, y + 1)) {
                return true;
            } else {
                matrix[x][y] = '.';
            }
        }

        return flag;

    }



    public List<Character> cc(char[][] matrix, int x, int y) {

        List<Character> list = new ArrayList<>(8);

        byte[] arr = new byte[9];

        for (int i = 0; i < 9; i++) {
            if (matrix[x][i] != '.') {
                arr[matrix[x][i] - 49] = 1;
            }

            if (matrix[i][y] != '.') {
                arr[matrix[i][y] - 49] = 1;
            }

        }

        int i = x / 3 * 3;
        int j = y / 3 * 3;

        for (int k = 0; k < 3; k++) {
            for (int m = 0; m < 3; m++) {
                if (matrix[k + i][m + j] != '.') {
                    arr[matrix[k + i][m + j] - 49] = 1;
                }
            }
        }

        for (int k = 0; k < 9; k++) {
            if (arr[k] != 1) {
                list.add((char) (k + 49));
            }
        }
        return list;
    }
}