174. Find the Town Judge

Easy · Graph

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 else (except 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] = [a, b]` means person `a` trusts person `b`. Return the label of the town judge if the town judge exists, otherwise return `-1`.

Examples

Example 1
Input: n = 3, trust = [[1,3],[2,3]]
Output: 3
Explanation: Person 3 is trusted by persons 1 and 2 (everyone else), and person 3 trusts nobody. So person 3 is the town judge.
Example 2
Input: n = 3, trust = [[1,3],[2,3],[3,1]]
Output: -1
Explanation: Person 3 trusts person 1, so person 3 cannot be the town judge.

Constraints