Optimize Duplicate Detection in Arrays

EasyPython

Problem

At Stripe, a service receives a list of integer event IDs and needs to quickly determine whether any ID appears more than once. A naive solution compares every pair of elements, but this is too slow for large inputs. Write an optimized algorithm to detect duplicates.

Formal Specification

Implement a function contains_duplicate(nums) that takes a list of integers nums and returns a boolean:

True if any value appears at least twice
False if all values are distinct

Constraints

1 <= len(nums) <= 10^5
-10^9 <= nums[i] <= 10^9
Input contains integers only
Target solution should improve on O(n^2) brute force

Function Signature

def contains_duplicate(nums):

CodePython 3

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