997. Find the Town Judge

Easy

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

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

解題

func findJudge(n int, trust [][]int) int {
    count := make([]int, n)

    for _, t := range trust {
        count[t[0] - 1]--
        count[t[1] - 1]++
    }

    for i, c := range count {
        if c == n - 1 { return i + 1 }
    }

    return -1
}