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Find Duplicate Number

Python data engineering interview problem. Difficulty: beginner. Pattern: Arrays. About 10 minutes. Part of the Pro drill bank.

Find the one duplicated number in 1..n with n+1 entries. Treat this as a production helper: match the contracted return shape, including empty and duplicate inputs.

Implement find_duplicate(nums: list) -> int where nums has n+1 integers in 1..n and exactly one duplicate.

Requirements

  • Exactly one duplicated number.

Constraints

  • Do not modify if using Floyd.

Examples

Input: find_duplicate([1, 3, 4, 2, 2]) Output: 2 2 appears twice.

Topics: lakebench, python, duplicate, floyd.

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beginner

Find Duplicate Number

Interview-style drill: Find the one duplicated number in 1..n with n+1 entries.

Implement `find_duplicate(nums: list) -> int` where nums has n+1 integers in 1..n and exactly one duplicate. Example: `[1, 3, 4, 2, 2]` → `2`. Keep the harness.