217.Contains_Duplicate.py

                        problem--------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.

Example 1:

Input: nums = [1,2,3,1]

Output: true

Explanation:

The element 1 occurs at the indices 0 and 3.

Example 2:

Input: nums = [1,2,3,4]

Output: false

Explanation:

All elements are distinct.

Example 3:

Input: nums = [1,1,1,3,3,4,3,2,4,2]

Output: true

 

Constraints:

1 <= nums.length <= 105
-109 <= nums[i] <= 109

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