217. Contains Duplicate-存在重复元素

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

Solution in python:

class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:
        aset = set()
        for item in nums:
            if item not in aset:
                aset.add(item)
            else:
                return True
        return False