Check if an array contains duplicates

Summary

Return True if any value appears more than once in the array, otherwise False.

Problem statement

Given a list arr, implement has_duplicates(arr) that returns True if there is at least one element that appears more than once, otherwise returns False. Use hashing (a set) to check efficiently: if the number of unique elements is less than the list length, duplicates exist.

Task

Implement has_duplicates(arr) to detect whether any duplicate exists using set size comparison for O(n) average time.

Examples

Input format

A list of hashable elements (e.g., integers), e.g., [1, 2, 3, 2]

Output format

A boolean: True if duplicates exist, False otherwise.

Constraints

0 <= len(arr) <= 10^5. Elements are hashable. Aim for O(n) average time and O(n) extra space.

Samples