LeetCode 997. Find the Town Judge

考點難度

Hash Table	Easy

題目

In a town, there are n people labeled from 1 to n. There is a rumor that one of these people is secretly the town judge.
If the town judge exists, then:
The town judge trusts nobody.
Everybody (except for the town judge) trusts the town judge.
There is exactly one person that satisfies properties 1 and 2.
You are given an array trust where trust[i] = [ai, bi] representing that the person labeled ai trusts the person labeled bi.
Return the label of the town judge if the town judge exists and can be identified, or return -1 otherwise.

思路

用一個array儲存所有人被trust - trust的結果（trust別人-1，被trust+1），最后遍歷array找到值為n-1的位置。

答案

class Solution {public int findJudge(int n, int[][] trust) {if(trust.length == 0){return n == 1 ? 1 : -1;}int[] trustCount = new int[n+1];for(int[] t : trust){trustCount[t[1]]++;trustCount[t[0]]--;}for(int i = 1; i < trustCount.length;i++){if(trustCount[i] == n-1)return i;}return -1;} }

總結

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