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Optimize Duplicate Detection in Arrays

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Your question is Optimize Duplicate Detection in Arrays. Start with the requirements on the right.

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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):
Your solutionPython 3
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