1958.检查操作是否合法

【LetMeFly】1958.检查操作是否合法:8个方向分别遍历

力扣题目链接:https://leetcode.cn/problems/check-if-move-is-legal/

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:

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:

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:

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' 。

解题方法:8个方向分别模拟

本题编号1958

思路

从修改位置开始向8个方向分别模拟,一旦某个方向符合“好线段”则返回true,全部模拟完未返回则返回false。

对于某个方向,要确保:

  1. 下一个格子是反色
  2. 之后的格子中,在遇到空格之前,遇到同色

具体细节

  1. 颜色的反色:color ^ 'W' ^ 'B'(这是因为两个相同值异或结果为0,0异或一个数结果为这个数);
  2. 其实可以不用真的修改rMove, cMove这个格子的颜色。

时空复杂度

  • 时间复杂度$O(CD)$。其中格子大小是$C\times C$,$C=8$;方向个数是$D$,$D=8$。
  • 空间复杂度$O(1)$

AC代码

C++

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const int directions[8][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}, {1, 1}, {1, -1}, {-1, 1}, {-1, -1}};
class Solution {
private:
inline bool inBorad(int x, int y) {
return x >= 0 && x < 8 && y >= 0 && y < 8;
}
public:
bool checkMove(vector<vector<char>>& board, int rMove, int cMove, char color) {
board[rMove][cMove] = color;
for (int d = 0; d < 8; d++) {
int x = rMove, y = cMove;
int dx = directions[d][0], dy = directions[d][1];
x += dx, y += dy;
if (!inBorad(x, y)) {
continue;
}
if (board[x][y] != (color ^ 'B' ^ 'W')) {
continue;
}
while (inBorad(x + dx, y + dy)) {
x = x + dx, y = y + dy;
if (board[x][y] == color) {
return true;
}
if (board[x][y] == '.') {
break;
}
}
}
return false;
}
};

/*
..W.BWWB
BW.W.WBB
.WBWW.WW
WW.W..BB
BWBBWWB.
W.W..BWW
B.BB..BB
.W.W.W.W

5 4 W
*/

Go

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package main

func inBoard(x int, y int) bool {
return 0 <= x && x < 8 && 0 <= y && y < 8
}

func checkMove(board [][]byte, rMove int, cMove int, color byte) bool {
directions := []struct{x, y int}{{0, 1}, {0, -1}, {1, 0}, {-1, 0}, {1, 1}, {1, -1}, {-1, 1}, {-1, -1}}
for _, thisDirection := range directions {
dx, dy := thisDirection.x, thisDirection.y
x, y := rMove + dx, cMove + dy
if !inBoard(x, y) || board[x][y] == '.' || board[x][y] == color {
continue
}
for inBoard(x + dx, y + dy) {
x, y = x + dx, y + dy
if board[x][y] == color {
return true
}
if board[x][y] == '.' {
break
}
}
}
return false
}

Java

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class Solution {
private static final int[][] directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}, {1, 1}, {1, -1}, {-1, 1}, {-1, -1}};

private boolean inBoard(int x, int y) {
return x >= 0 && x < 8 && y >= 0 && y < 8;
}

public boolean checkMove(char[][] board, int rMove, int cMove, char color) {
for (int d = 0; d < 8; d++) {
int dx = directions[d][0], dy = directions[d][1];
int x = rMove + dx, y = cMove + dy;
if (!inBoard(x, y) || board[x][y] == '.' || board[x][y] == color) {
continue;
}
while (inBoard(x + dx, y + dy)) {
x = x + dx;
y = y + dy;
if (board[x][y] == color) {
return true;
}
if (board[x][y] == '.') {
break;
}
}
}
return false;
}
}

Python

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from typing import List

DIRECTIONS = [[0, 1], [0, -1], [1, 0], [-1, 0], [1, 1], [1, -1], [-1, 1], [-1, -1]]

class Solution:
def inBoard(self, x: int, y: int) -> bool:
return 0 <= x < 8 and 0 <= y < 8

def checkMove(self, board: List[List[str]], rMove: int, cMove: int, color: str) -> bool:
board[rMove][cMove] = color # 其实不真的修改也没问题
for tx, ty in DIRECTIONS:
x, y = rMove + tx, cMove + ty
if not self.inBoard(x, y):
continue
if board[x][y] == color or board[x][y] == '.':
continue
while self.inBoard(x + tx, y + ty):
x, y = x + tx, y + ty
if board[x][y] == color:
return True
if board[x][y] == '.':
break
return False

同步发文于CSDN和我的个人博客,原创不易,转载经作者同意后请附上原文链接哦~

Tisfy:https://letmefly.blog.csdn.net/article/details/140249215


1958.检查操作是否合法
https://blog.letmefly.xyz/2024/07/07/LeetCode 1958.检查操作是否合法/
作者
Tisfy
发布于
2024年7月7日
许可协议