# Solution: Contains Duplicate (Python)

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.

Check it out: https://leetcode.com/problems/contains-duplicate/

**Example 1:**

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

**Output:** true

**Example 2:**

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

**Output:** false

**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:**

`class Solution:`

def containsDuplicate(self, nums: List[int]) -> bool:

if len(nums)==len(set(nums)):

return False

else:

return True

**Explanation:**

Here we make use of **Sets in Python**. A Set is an unordered collection data type that is iterable, mutable, and has no duplicate elements. 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, we can make use of Sets to make sure that the elements in the list are unique. When the elements in the given array are already unique, converting it into a set does not make any difference, and hence both the length remains the same. **So we can conclude that, if the length of the array and the length of the set is equal, then the array does not have any duplicate elements, hence returning ****true**** as per requirements. Alternatively, if the length of the array and the set differs, then it means that duplicate elements were found in the array, hence returning ****false .**