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. 1.
    The town judge trusts nobody.
  2. 2.
    Everybody (except for the town judge) trusts the town judge.
  3. 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
}