Description: 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.

Brute-force Approach

Iterate through the array and for each element, iterate through the rest of the array to check for duplicates.

Time: O(n^2)

Space: O(1)

Better Approach

Sort the array and iterate through it, checking for duplicate neighbors.

Time: O(nlogn)

Space: O(1)

Optimal Approach

Iterate through the array and add the elements to a hash set. If an element already exists, return true. Can also be done using a hashmap.

Time: O(n)

Space: O(n)