Leetcode 0997. Find the Town Judge

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.

Easy

Description

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.

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

Constraints:

• 1 <= n <= 1000
• 0 <= trust.length <= 10^4
• trust[i].length == 2
• All the pairs of trust are unique.
• ai != bi
• 1 <= ai, bi <= n

Solution

class Solution {
    public int findJudge(int n, int[][] trust) {
        int arr[] = new int[n+1];

        for(int i = 0; i < trust.length; i++){
            arr[trust[i][0]]--;
            arr[trust[i][1]]++;
        }

        for(int i = 1; i < arr.length; i++){
            if(arr[i] == n-1) return i;
        }

        return -1;
    }
}