检查操作是否合法

2024-07-07

题目：

给你一个下标从 0 开始的 8 x 8 网格 board ，其中 board[r][c] 表示游戏棋盘上的格子 (r, c) 。棋盘上空格用 '.' 表示，白色格子用 'W' 表示，黑色格子用 'B' 表示。

游戏中每次操作步骤为：选择一个空格子，将它变成你正在执行的颜色（要么白色，要么黑色）。但是，合法 操作必须满足：涂色后这个格子是 好线段的一个端点 （好线段可以是水平的，竖直的或者是对角线）。

好线段 指的是一个包含 三个或者更多格子（包含端点格子）的线段，线段两个端点格子为 同一种颜色 ，且中间剩余格子的颜色都为 另一种颜色 （线段上不能有任何空格子）。你可以在下图找到好线段的例子：

img

给你两个整数 rMove 和 cMove 以及一个字符 color ，表示你正在执行操作的颜色（白或者黑），如果将格子 (rMove, cMove) 变成颜色 color 后，是一个 合法 操作，那么返回 true ，如果不是合法操作返回 false 。

示例 1：

img

输入：board = [[".",".",".","B",".",".",".","."],[".",".",".","W",".",".",".","."],[".",".",".","W",".",".",".","."],[".",".",".","W",".",".",".","."],["W","B","B",".","W","W","W","B"],[".",".",".","B",".",".",".","."],[".",".",".","B",".",".",".","."],[".",".",".","W",".",".",".","."]], rMove = 4, cMove = 3, color = "B"
输出：true
解释：'.'，'W' 和 'B' 分别用颜色蓝色，白色和黑色表示。格子 (rMove, cMove) 用 'X' 标记。
以选中格子为端点的两个好线段在上图中用红色矩形标注出来了。

示例 2：

img

输入：board = [[".",".",".",".",".",".",".","."],[".","B",".",".","W",".",".","."],[".",".","W",".",".",".",".","."],[".",".",".","W","B",".",".","."],[".",".",".",".",".",".",".","."],[".",".",".",".","B","W",".","."],[".",".",".",".",".",".","W","."],[".",".",".",".",".",".",".","B"]], rMove = 4, cMove = 4, color = "W"
输出：false
解释：虽然选中格子涂色后，棋盘上产生了好线段，但选中格子是作为中间格子，没有产生以选中格子为端点的好线段。

提示：

  • board.length == board[r].length == 8
  • 0 <= rMove, cMove < 8
  • board[rMove][cMove] == '.'
  • color 要么是 'B' 要么是 'W' 。

思路：

这道题就是题目长，实际比较简单

由于我们只需要判断操作是否合法， 其实就是判断是否存在一条从(rMove, cMove)开始的好线段， 那么就需要判断8个方向。

在每个方向上判断是否存在好线段，及好线段长度是否 >= 3 即可

代码：

class Solution {
public:
    int dire[8][2] = { {1, 0}, {-1, 0}, {0, 1}, {0, -1}, {1, 1}, {1, -1}, {-1, 1}, {-1, -1} };
    bool isValidPath(vector<vector<char>>& board, int idx, int rMove, int cMove, char color) {
        int pathLen = 1;
        int nextRow = rMove + dire[idx][0], nextCol = cMove + dire[idx][1];
        while (nextRow >= 0 && nextRow < 8 && nextCol >= 0 && nextCol < 8) {
            if (board[nextRow][nextCol] == color) {
                return pathLen >= 2;
            }else if (board[nextRow][nextCol] == '.') {
                return false;
            }else {
                pathLen++;
                nextRow += dire[idx][0];
                nextCol += dire[idx][1];
            }
        }
        return false;
    }
    bool checkMove(vector<vector<char>>& board, int rMove, int cMove, char color) {
        for (int i = 0; i < 8; i++) {
            if (isValidPath(board, i, rMove, cMove, color)) {
                return true;
            }
        }
        return false;
    }
};