LeetCode DSA Series #4: 217. Contains Duplicate

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

You can find the problem here.

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

Time and space complexity are O(N).