Given an array of integers, find if the array contains any duplicates.

Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Example 1:

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

Example 2:

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

Example 3:

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

給定一個整數數組，判斷是否存在重復元素。

如果任何值在數組中出現至少兩次，函數返回 true。如果數組中每個元素都不相同，則返回 false。

示例 1:

輸入: [1,2,3,1]
輸出: true

示例 2:

輸入: [1,2,3,4]
輸出: false

示例 3:

輸入: [1,1,1,3,3,4,3,2,4,2]
輸出: true

 1 class Solution {
 2     func containsDuplicate(_ nums: [Int]) -> Bool {
 
 3         if nums == nil || nums.count == 0 {return false}
 4         var array:[Int] = nums
 5         //先排序
 6         array.sort(){$0 < $1}
 7         //再遍歷
 8         for i in 0..<(array.count-1)
 9         {
10             if array[i] == array[i+1]
11             {
12                 return
 
 true
13             }
14         }
15         return false
16     }
17 }

36ms

 1 class Solution {
 2     func containsDuplicate(_ nums: [Int]) -> Bool {
 3         var set = Set<Int>()
 4         
 5         for index in nums.indices where !set.insert(nums[index]).inserted{
 6             return true
 7         }
 8         return false
 9     }
10 }

40ms

1 class Solution {
2     func containsDuplicate(_ nums: [Int]) -> Bool {
3         var set = Set(nums)
4         return set.count != nums.count
5     }
6 }

217. 存在重復元素 | Contains Duplicate