[Swift]LeetCode961. 重複 N 次的元素 | N-Repeated Element in Size 2N Array

★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★
➤微信公衆號：山青詠芝（shanqingyongzhi）
➤博客園地址：山青詠芝（https://www.cnblogs.com/strengthen/）
➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：http://www.javashuo.com/article/p-dkwiayir-me.html 
➤若是連接不是山青詠芝的博客園地址，則多是爬取做者的文章。
➤原文已修改更新！強烈建議點擊原文地址閱讀！支持做者！支持原創！
★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★

In a array A of size 2N, there are N+1 unique elements, and exactly one of these elements is repeated N times.

Return the element repeated N times.

Example 1:

Input: [1,2,3,3]
Output: 3 

Example 2:

Input: [2,1,2,5,3,2]
Output: 2 

Example 3:

Input: [5,1,5,2,5,3,5,4]
Output: 5

Note:

1. 4 <= A.length <= 10000
2. 0 <= A[i] < 10000
3. A.length is even

---

在大小爲 2N 的數組 A 中有 N+1 個不一樣的元素，其中有一個元素重複了 N 次。

返回重複了 N 次的那個元素。

示例 1：

輸入：[1,2,3,3]
輸出：3

示例 2：

輸入：[2,1,2,5,3,2]
輸出：2

示例 3：

輸入：[5,1,5,2,5,3,5,4]
輸出：5

提示：

1. 4 <= A.length <= 10000
2. 0 <= A[i] < 10000
3. A.length 爲偶數

---

276ms

 1 class BitVector {
 2   private let wordSize: Int = 64
 3   var vector: [Int]
 4   
 5   init(size: Int) {
 6     let count = abs(size/wordSize)+1
 7     vector = Array(repeating: 0, count: count)
 8   }
 9   
10   func setBit(int: Int) -> Bool {
11     let wordIndex = abs(int/wordSize)
12     let word = vector[wordIndex]
13     let mask = 1 << (int%wordSize)
14       
15     if word & mask != 0 {
16       return false
17     } else {
18       vector[wordIndex] = word | mask
19     }
20     return true
21   }
22 }
23 
24 class Solution {
25     func repeatedNTimes(_ A: [Int]) -> Int {
26         let bitVector = BitVector(size: 10000)
27         for a in A {
28             if !bitVector.setBit(int: a) {
29                 return a
30             }
31         }
32         return -1
33     }
34 }

---

280ms

 1 class Solution {
 2     func repeatedNTimes(_ A: [Int]) -> Int {
 3         var dict : [Int: Int] = [:]
 4         for i in A {
 5             dict[i] = (dict[i] ?? 0) + 1
 6             if dict[i] == 2 {
 7                 return i
 8             }
 9         }
10         return -1
11     }
12 }

---

280ms

 1 class Solution {
 2     func repeatedNTimes(_ A: [Int]) -> Int {
 3         var set:Set<Int> = Set<Int>()
 4         for x in A
 5         {
 6             if set.contains(x)
 7             {
 8                 return x
 9             }
10             set.insert(x)
11         }
12         return -1
13     }
14 }

---

300ms 

 1 class Solution {
 2     func repeatedNTimes(_ A: [Int]) -> Int {
 3         var n:Int = A.count
 4         var f:[Int] = [Int](repeating:0,count:100000)
 5         for v in A
 6         {
 7             f[v] += 1
 8         }
 9         
10         for i in 0..<100000
11         {
12             if f[i] > 1
13             {
14                 return i
15             }
16         }
17         return -1
18     }
19 }

---

316ms

 

 1 class Solution {
 2     func repeatedNTimes(_ A: [Int]) -> Int {
 3         let aDict = Dictionary( A.map{ ($0, 1) }, uniquingKeysWith: +)
 4         for (key, value) in aDict {
 5             if value >= 2 {
 6                 return key
 7             }
 8         }
 9         return -1
10     }
11 }

---

336ms

1 class Solution {
2     func repeatedNTimes(_ A: [Int]) -> Int {
3         var counts = [Int : Int]()
4         
5         A.forEach( { counts[$0, default: 0] += 1 })
6         
7         return counts.max(by: {a, b in a.value < b.value })!.key
8     }
9 }

---

396ms

 1 class Solution {
 2     func repeatedNTimes(_ A: [Int]) -> Int {
 3        
 4         var numSet : Set<Int> = []
 5         
 6         for num in A.sorted()[0...A.count/2+1]
 7         {
 8             if numSet.contains(num)
 9             {
10                 return num
11             }
12             numSet.insert(num)
13         }
14         return 0
15     }
16 }