#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
class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:
        # return not len(set(nums))==len(nums)
        
        ##hash table
        appeared = set()
        for i in nums:
            if i in appeared:
                return True
            else: appeared.add(i)
        return False