[leetcode] 1496. Path Crossing

[leetcode] 1496. Path Crossing

Description

Given a string path, where path[i] = ‘N’, ‘S’, ‘E’ or ‘W’, each representing moving one unit north, south, east, or west, respectively. You start at the origin (0, 0) on a 2D plane and walk on the path specified by path.

Return True if the path crosses itself at any point, that is, if at any time you are on a location you’ve previously visited. Return False otherwise.

Example 1:

Input: path = "NES"Output: false Explanation: Notice that the path doesn't cross any point more than once.

Example 2:

Input: path = "NESWW"Output: trueExplanation: Notice that the path visits the origin twice.

Constraints:

1 <= path.length <= 10^4path will only consist of characters in {‘N’, ‘S’, ‘E’, 'W}

分析

题目的意思是：给定一个字符串表示点的移动方向，判断这个点的轨迹是否交叉。我看了一下提示，思路大概是这样，用points记录点走过的坐标，然后遍历判断当前的坐标是否在points里面就行了，如果是则找到了，返回True，否则返回False。

代码

class Solution: def isPathCrossing(self, path: str) -> bool: x=0 y=0 points=[[0,0]] for ch in path: if(ch=='N'): y+=1 elif(ch=='S'): y-=1 elif(ch=='E'): x+=1 elif(ch=='W'): x-=1 if([x,y] in points): return True else: points.append([x,y]) return False

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