{"id":6993,"date":"2020-06-28T00:41:25","date_gmt":"2020-06-28T07:41:25","guid":{"rendered":"https:\/\/zxi.mytechroad.com\/blog\/?p=6993"},"modified":"2020-06-28T00:42:35","modified_gmt":"2020-06-28T07:42:35","slug":"leetcode-1496-path-crossing","status":"publish","type":"post","link":"https:\/\/zxi.mytechroad.com\/blog\/hashtable\/leetcode-1496-path-crossing\/","title":{"rendered":"\u82b1\u82b1\u9171 LeetCode 1496. Path Crossing"},"content":{"rendered":"\n

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

Return True<\/code> 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<\/code> otherwise.<\/p>\n\n\n\n

Example 1:<\/strong><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
Input:<\/strong> path = \"NES\"\nOutput:<\/strong> false \nExplanation:<\/strong> Notice that the path doesn't cross any point more than once.\n<\/pre>\n\n\n\n
Example 2:<\/strong><\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Input:<\/strong> path = \"NESWW\"\nOutput:<\/strong> true\nExplanation:<\/strong> Notice that the path visits the origin twice.<\/pre>\n\n\n\n
Constraints:<\/strong><\/p>\n\n\n\n
  • 1 <= path.length <= 10^4<\/code><\/li>
  • path<\/code> will only consist of characters in {'N', 'S', 'E', 'W}<\/code><\/li><\/ul>\n\n\n\n
    Solution: Simulation + Hashtable<\/strong><\/h2>\n\n\n\n
    Time complexity: O(n)
    Space complexity: O(n)<\/p>\n\n\n\n
    \n
    C++<\/h2>\n
    \n\n
    \n\/\/ Author: Huahua\nclass Solution {\npublic:\n  bool isPathCrossing(string path) {\n    unordered_set s;\n    int x = 0;\n    int y = 0;\n    s.insert(x * 10000 + y);\n    for (char d : path) {\n      if (d == 'N') ++y;\n      else if (d == 'S') --y;\n      else if (d == 'E') ++x;\n      else if (d == 'W') --x;\n      if (!s.insert(x * 10000 + y).second)\n        return true;\n    }\n    return false;\n  }\n};\n<\/pre>\n<\/div><\/div>\n\n\n\n
    <\/p>\n","protected":false},"excerpt":{"rendered":"
    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…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[70],"tags":[222,82,179],"class_list":["post-6993","post","type-post","status-publish","format-standard","hentry","category-hashtable","tag-easy","tag-hashtable","tag-simulation","entry","simple"],"_links":{"self":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6993","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/comments?post=6993"}],"version-history":[{"count":2,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6993\/revisions"}],"predecessor-version":[{"id":6995,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/6993\/revisions\/6995"}],"wp:attachment":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/media?parent=6993"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/categories?post=6993"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/tags?post=6993"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}