Contains Duplicate
Given an integer array, determine if any value appears at least twice in the array.
Write a function that returns true if any value appears at least twice in the array, and false if every element is distinct.
How to Solve
Use a Set to track seen numbers. As you iterate through the array, if a number is already in the set, return true. Otherwise, add it to the set. If you finish iterating without finding duplicates, return false.
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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