{"id":4885,"date":"2019-02-23T23:05:15","date_gmt":"2019-02-24T07:05:15","guid":{"rendered":"https:\/\/zxi.mytechroad.com\/blog\/?p=4885"},"modified":"2019-02-23T23:05:48","modified_gmt":"2019-02-24T07:05:48","slug":"leetcode-997-find-the-town-judge","status":"publish","type":"post","link":"https:\/\/zxi.mytechroad.com\/blog\/graph\/leetcode-997-find-the-town-judge\/","title":{"rendered":"\u82b1\u82b1\u9171 LeetCode 997. Find the Town Judge"},"content":{"rendered":"\n

In a town, there are N<\/code> people labelled from 1<\/code> to N<\/code>.  There is a rumor that one of these people is secretly the town judge.<\/p>\n\n\n\n

If the town judge exists, then:<\/p>\n\n\n\n

  1. The town judge trusts nobody.<\/li>
  2. Everybody (except for the town judge) trusts the town judge.<\/li>
  3. There is exactly one person that satisfies properties 1 and 2.<\/li><\/ol>\n\n\n\n

    You are given trust<\/code>, an array of pairs trust[i] = [a, b]<\/code> representing that the person labelled a<\/code> trusts the person labelled b<\/code>.<\/p>\n\n\n\n

    If the town judge exists and can be identified, return the label of the town judge.  Otherwise, return -1<\/code>.<\/p>\n\n\n\n

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

    Input: <\/strong>N = 2, trust = [[1,2]]\nOutput: <\/strong>2\n<\/pre>\n\n\n\n
    Example 2:<\/strong><\/p>\n\n\n\n
    Input: <\/strong>N = 3, trust = [[1,3],[2,3]]\nOutput: <\/strong>3\n<\/pre>\n\n\n\n
    Example 3:<\/strong><\/p>\n\n\n\n
    Input: <\/strong>N = 3, trust = [[1,3],[2,3],[3,1]]\nOutput: <\/strong>-1\n<\/pre>\n\n\n\n
    Example 4:<\/strong><\/p>\n\n\n\n
    Input: <\/strong>N = 3, trust = [[1,2],[2,3]]\nOutput: <\/strong>-1\n<\/pre>\n\n\n\n
    Example 5:<\/strong><\/p>\n\n\n\n
    Input: <\/strong>N = 4, trust = [[1,3],[1,4],[2,3],[2,4],[4,3]]\nOutput: <\/strong>3<\/pre>\n\n\n\n
    Note:<\/strong><\/p>\n\n\n\n
    1. 1 <= N <= 1000<\/code><\/li>
    2. trust.length <= 10000<\/code><\/li>
    3. trust[i]<\/code> are all different<\/li>
    4. trust[i][0] != trust[i][1]<\/code><\/li>
    5. 1 <= trust[i][0], trust[i][1] <= N<\/code><\/li><\/ol>\n\n\n\n
      Solution: Degree<\/strong><\/h2>\n\n\n\n
      node with degree (in_degree – out_degree) N – 1 is the judge.<\/p>\n\n\n\n
      Time complexity: O(N+T)
      Space complexity: O(N)<\/p>\n\n\n\n
      \n
      C++<\/h2>\n
      \n\n
      \nclass Solution {\npublic:\n  int findJudge(int N, vector>& trusts) {    \n    vector degrees(N + 1);    \n    for (const auto& trust : trusts) {\n      --degrees[trust[0]];\n      ++degrees[trust[1]];\n    }\n    for (int i = 1; i <= N; ++i)\n      if (degrees[i] == N - 1) return i;\n    return -1;\n  }\n};\n<\/pre>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
      In a town, there are N people labelled from 1 to N.  There is a rumor that one of these people is secretly the town judge. If the town judge exists,…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[76],"tags":[244,222,77],"class_list":["post-4885","post","type-post","status-publish","format-standard","hentry","category-graph","tag-degree","tag-easy","tag-graph","entry","simple"],"_links":{"self":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/4885","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=4885"}],"version-history":[{"count":2,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/4885\/revisions"}],"predecessor-version":[{"id":4887,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/posts\/4885\/revisions\/4887"}],"wp:attachment":[{"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/media?parent=4885"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/categories?post=4885"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zxi.mytechroad.com\/blog\/wp-json\/wp\/v2\/tags?post=4885"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}