997. 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
Constraints:
1 <= N <= 10000 <= trust.length <= 10^4trust[i].length == 2trust[i]are all differenttrust[i][0] != trust[i][1]1 <= trust[i][0], trust[i][1] <= N
Rust Solution
struct Solution;
impl Solution {
fn find_judge(n: i32, trust: Vec<Vec<i32>>) -> i32 {
let n = n as usize;
let mut degree = vec![0; n];
for edge in trust {
let u = (edge[0] - 1) as usize;
let v = (edge[1] - 1) as usize;
degree[v] += 1;
degree[u] -= 1;
}
for i in 0..n {
if degree[i] as usize == n - 1 {
return (i + 1) as i32;
}
}
-1
}
}
#[test]
fn test() {
let n = 2;
let trust = vec_vec_i32![[1, 2]];
let res = 2;
assert_eq!(Solution::find_judge(n, trust), res);
let n = 3;
let trust = vec_vec_i32![[1, 3], [2, 3]];
let res = 3;
assert_eq!(Solution::find_judge(n, trust), res);
let n = 3;
let trust = vec_vec_i32![[1, 3], [2, 3], [3, 1]];
let res = -1;
assert_eq!(Solution::find_judge(n, trust), res);
let n = 3;
let trust = vec_vec_i32![[1, 2], [2, 3]];
let res = -1;
assert_eq!(Solution::find_judge(n, trust), res);
let n = 4;
let trust = vec_vec_i32![[1, 3], [1, 4], [2, 3], [2, 4], [4, 3]];
let res = 3;
assert_eq!(Solution::find_judge(n, trust), res);
}
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