997. Find the Town Judge
https://leetcode.com/problems/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:
- The town judge trusts nobody.
- Everybody (except for the town judge) trusts the town judge.
- 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
Note:
1 <= N <= 1000trust.length <= 10000trust[i]are all differenttrust[i][0] != trust[i][1]1 <= trust[i][0], trust[i][1] <= N
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Intuition
The town judge will be trusted by N - 1 people, => increment count for people if they are at position 2 (index 1) on the trust array row
People can trust each other as well, in addition to trusting judge => decrement count for person at position 1 (index 0) on the trust array row
Ex 5 - 1 trusts 3, 4
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Time - O(N) = O(|V|)
Space - O(N) = O(|V|)
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