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.

LeetCode: Contains Duplicate

Example:

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

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

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

Hints

Hint 1

Think about using a data structure that can track what you've seen so far. What has O(1) lookup time?

Hint 2

As you iterate through the array, check if each element is already in your set. If yes, you found a duplicate.

Hint 3

Alternatively, you could sort the array first and check adjacent elements. But is that more or less efficient?