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:

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 `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 <= 1000`
• `0 <= trust.length <= 10^4`
• `trust[i].length == 2`
• `trust[i]` are all different
• `trust[i][0] != trust[i][1]`
• `1 <= trust[i][0], trust[i][1] <= N`

997. Find the Town Judge
``````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);
}
``````