217. Contains Duplicate

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

思路：遍历nums，把num插入集合，如果集合中有，就说明出现次数多于一次，返回True，遍历完，返回False

代码：python3

class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:
        numSet = set()
        for n in nums:
            if n in numSet:
                return True
            else:
                numSet.add(n)
        return False