1496. Path Crossing
https://leetcode.com/problems/path-crossing/
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 <= 10^4pathwill only consist of characters in{'N', 'S', 'E', 'W}
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| class Solution { | |
| public boolean isPathCrossing(String path) { | |
| Set<String> visited = new HashSet<String>(); | |
| int r = 0, c = 0; | |
| visited.add(r + "," + c); | |
| for (int i = 0; i < path.length(); i++) { | |
| char ch = path.charAt(i); | |
| switch (ch) { | |
| case 'N': | |
| r--; | |
| break; | |
| case 'E': | |
| c++; | |
| break; | |
| case 'W': | |
| c--; | |
| break; | |
| case 'S': | |
| r++; | |
| } | |
| String key = r + "," + c; | |
| if (visited.contains(key)) { | |
| return true; | |
| } | |
| visited.add(key); | |
| } | |
| return false; | |
| } | |
| } |
