# 997. Find the Town Judge

## 1. Question

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:

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 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.

## 2. Examples

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


## 3. Constraints

• 1 <= n <= 1000
• 0 <= trust.length <= 104
• trust[i].length == 2
• All the pairs of trust are unique.
• ai != bi
• 1 <= ai, bi <= n

## 5. Solutions

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

for(int[] arr : trust) {
out[arr[0]]++;
in[arr[1]]++;
}

for(int i = 1; i <= n; i++) {
if(in[i] == n - 1 && out[i] == 0) {
return i;
}
}
return -1;
}
}