1496. Path Crossing

Problem Link

Description

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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 have 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 <= 104
• path[i] is either 'N', 'S', 'E', or 'W'.

Solution

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Python3

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