Find the Town Judge

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:

1. The town judge trusts nobody.

2. Everybody (except for the town judge) trusts the town judge.

3. 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

Constraints:

• 1 <= N <= 1000

• 0 <= trust.length <= 10^4

• trust[i].length == 2

• trust[i] are all different

• trust[i][0] != trust[i][1]

• 1 <= trust[i][0], trust[i][1] <= N

class Solution {
    public int findJudge(int N, int[][] trust) {
        // count[i] -> Total number of incoming connections - total of 
        // outgoing connections for node i
        int[] count = new int[N + 1];
        for (int[] t : trust) {
            count[t[0]]--;
            count[t[1]]++;
        }
        for (int i = 1; i <= N; ++i) {
            if (count[i] == N - 1)
                return i;
        }
        return -1;
    }
}