[游戏开发]LeetCode-37解数独-困难

标题：37解数独-困难

题目

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1

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"]]

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

代码Java

public void solveSudoku(char[][] board) {
    backTracking(board);
}

public boolean backTracking(char[][] board) {
    for (int i = 0; i < 9; i++) {
        for (int j = 0; j < 9; j++) {
            if (board[i][j] != '.') continue;
            for (char k = '1'; k <= '9'; k++) {
                if (isVaild(i, j, board, k)) {
                    board[i][j] = k;
                    if (backTracking(board)) return true;
                    board[i][j] = '.';
                }
            }
            return false;
        }
    }
    return true;
}


public boolean isVaild(int row, int col, char[][] board, char val) {
    // 验证val在行上是否 有效
    for (int i = 0; i < 9; i++) {
        if (board[row][i] == val)
            return false;
    }
    // 验证val在列上是否 有效
    for (int i = 0; i < 9; i++) {
        if (board[i][col] == val)
            return false;
    }
    // 验证所在3*3方格内是否 有效
    // 所在方格位置的方格内第一个
    int x = (row / 3) * 3;
    int y = (col / 3) * 3;
    for (int i = x; i < x + 3; i++) {
        for (int j = y; j < y + 3; j++) {
            if (board[i][j] == val)
                return false;
        }
    }
    return true;
}