Problem Statement

You are given a town with n people, labeled from 1 to n. Some people trust others. You need to find out if there is a "town judge". The town judge is someone who:

1. Everyone else trusts.
2. The town judge trusts nobody.

Given n and an array trust, where trust[i] = [a_i, b_i] means person a_i trusts person b_i, return the label of town judge. If there is no town judge, return -1.

Examples

Example 1:

• Input: n = 4, trust = [[1, 2], [3, 2], [4, 2]]
• Expected Output: 2
• Justification: Person 2 is trusted by persons 1, 3, and 4, and person 2 trusts no one. Hence, person 2 is the town judge.

Example 2:

• Input: n = 3, trust = [[1, 3], [2, 3]]
• Expected Output: 3
• Justification: Person 3 is trusted by persons 1 and 2, and person 3 trusts no one. Hence, person 3 is the town judge.

Example 3:

• Input: n = 3, trust = [[1, 3], [2, 1], [3, 1]]
• Expected Output: -1
• Justification: Person 1 is trusted by persons 2 and 3, but person 1 also trusts person 3. Thus, there is no town judge.

Constraints:

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

Try it yourself

Try solving this question here: