Find the Town Judge

Similar Problems:

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, 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 trust, an array of pairs trust[i] = [a, b] representing that the person labelled a trusts the person labelled b.

If the town judge exists and can be identified, return the label of the town judge. Otherwise, return -1.

Example 1:

Input: N = 2, trust = [[1,2]] Output: 2

Example 2:

Input: N = 3, trust = [[1,3],[2,3]] Output: 3

Example 3:

Input: N = 3, trust = [[1,3],[2,3],[3,1]] Output: -1

Example 4:

Input: N = 3, trust = [[1,2],[2,3]] Output: -1

Example 5:

Input: N = 4, trust = [[1,3],[1,4],[2,3],[2,4],[4,3]] Output: 3

Note:

- 1 <= N <= 1000
- trust.length <= 10000
- trust[i] are all different
- trust[i][0] != trust[i][1]
- 1 <= trust[i][0], trust[i][1] <= N

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

// https://code.dennyzhang.com/find-the-town-judge // Basic Ideas: array // l[i]: how many people trust me. If I trust anyone, I'm not the candidate. Mark it as -1 // Complexity: Time O(n), Space O(n) func findJudge(N int, trust [][]int) int { l := make([]int, N+1) for _, t := range trust { t1, t2 := t[0], t[1] l[t1] = -1 if l[t2] != -1 { l[t2]++ } } for i:=1; i<=N; i++ { if l[i] == N-1 { return i } } return -1 }