[Swift]LeetCode997. 找到小镇的法官 | Find the Town Judge

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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

Note:

1. 1 <= N <= 1000
2. trust.length <= 10000
3. trust[i] are all different
4. trust[i][0] != trust[i][1]
5. 1 <= trust[i][0], trust[i][1] <= N

---

在一个小镇里，按从 1 到 N 标记了 N 个人。传言称，这些人中有一个是小镇上的秘密法官。

如果小镇的法官真的存在，那么：

1. 小镇的法官不相信任何人。
2. 每个人（除了小镇法官外）都信任小镇的法官。
3. 只有一个人同时满足属性 1 和属性 2 。

给定数组 trust，该数组由信任对 trust[i] = [a, b] 组成，表示标记为 a 的人信任标记为 b 的人。

如果小镇存在秘密法官并且可以确定他的身份，请返回该法官的标记。否则，返回 -1。 

示例 1：

输入：N = 2, trust = [[1,2]]
输出：2

示例 2：

输入：N = 3, trust = [[1,3],[2,3]]
输出：3

示例 3：

输入：N = 3, trust = [[1,3],[2,3],[3,1]]
输出：-1

示例 4：

输入：N = 3, trust = [[1,2],[2,3]]
输出：-1

示例 5：

输入：N = 4, trust = [[1,3],[1,4],[2,3],[2,4],[4,3]]
输出：3 

提示：

1. 1 <= N <= 1000
2. trust.length <= 10000
3. trust[i] 是完全不同的
4. trust[i][0] != trust[i][1]
5. 1 <= trust[i][0], trust[i][1] <= N

---

776ms

class Solution {    
    func findJudge(_ N: Int, _ trust: [[Int]]) -> Int {
       if( N == 1) {
        return N
    }
    if(trust.count == 0 || trust[0].count==0){
         return -1;
    }
    var vote = [Int](repeating: 0, count: N)
    for i in 0..<trust.count {
        var trustee = trust[i][0] //someone is a trustee
        var trusted = trust[i][1] // Trusted by someone
        vote[trustee - 1] =  vote[trustee - 1] - 1
        vote[trusted - 1] =  vote[trusted - 1] + 1
    }
    for i in 0..<N{
        if(vote[i] == N-1) {
            return i + 1
        }
    }
    return -1
  }
}

---

784ms

class Solution {
    func findJudge(_ N: Int, _ trust: [[Int]]) -> Int {
        var arr = Array(repeating: 0, count: N + 1)
        for i in 0..<trust.count {
            arr[trust[i][1]] += 1
            arr[trust[i][0]] -= 1
        }
        for i in 1..<arr.count {
            if arr[i] == N - 1 {return i}
        }
        return -1
    }
}

---

788ms

class Solution {
  func findJudge(_ N: Int, _ trust: [[Int]]) -> Int {
    var res = [Int].init(repeating: 0, count: N)
    var trusts = [Bool].init(repeating: false, count: N)
    for pair in trust { 
      res[pair[1] - 1] += 1
      trusts[pair[0] - 1] = true
    }
    
    for i in 0..<N {
      if res[i] == N - 1 && trusts[i] == false {
        return i + 1
      }
    }
    return -1
  }
}

---

800ms

class Solution {
    func findJudge(_ N: Int, _ trust: [[Int]]) -> Int {
        var candDict: [Int: Int] = [:]
        for index in 1...N+1{
            candDict[index] = 0
        }
        for tru in trust{
            var t = tru[0]
            var r = tru[1]
            if let val = candDict[t]{
                candDict[t] = nil
            }
            if let val = candDict[r]{
                candDict[r]! += 1
            }
        }
        for (key,val) in candDict{
            if val == N-1{
                return key
            }
        }
        return -1
    }
}

---

816ms

class Solution {
    func findJudge(_ N: Int, _ trust: [[Int]]) -> Int {
        var inAndOut = [[Int]](repeating: [Int](repeating: 0, count: 2),count: N + 1)
        for t in trust {
            inAndOut[t[0]][0] += 1
            inAndOut[t[1]][1] += 1
        }
        
        for i in 1..<inAndOut.count {
            let item = inAndOut[i]
            if item[1] == N - 1 && item[0] == 0 {
                return  i
            }
        }
        return -1
    }
}