題目如下：

Given a stringpath, wherepath[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 bypath.

ReturnTrueif the path crosses itself at any point, that is, if at any time you are on a location you've previously visited. ReturnFalse

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
• pathwill only consist of characters in{'N', 'S', 'E', 'W}

解題思路：送分題。

程式碼如下：

class Solution(object):
    def isPathCrossing(self, path):
        """
        :type path: str
        :rtype: bool
        """
        visit = {}
        x,y = 0,0
        visit[(x,y)] = 1
        for i in path:
            if i == 'N':
                y -= 1
            elif i == '
 
S':
                y += 1
            elif i == 'E':
                x += 1
            else:x -= 1
            if (x,y) in visit:return True
            visit[(x,y)] = 1
        return False