1496. Path Crossing-判断路径是否相交

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: true
Explanation: Notice that the path visits the origin twice.

Constraints:

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

Solution in python:

class Solution:
    def isPathCrossing(self, path: str) -> bool:
        aset = set()
        aset.add("0,0")
        x, y = 0, 0
        for it in path:
            if it == 'N':
                y += 1
            if it == 'S':
                y -= 1
            if it == 'E':
                x += 1
            if it == 'W':
                x -= 1
            temp = str(x)+","+str(y)
            if temp in aset:
                return True
            else:
                aset.add(temp)
                print(aset)
        return False