0997. Find the Town Judge

https://leetcode.com/problems/find-the-town-judge

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:

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.

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 <= 104

• trust[i].length == 2

• All the pairs of trust are unique.

• ai != bi

• 1 <= ai, bi <= n

ac