CodingHardcod-p041

Subject Two pointersLevel Senior–Staff~35 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

An array of n+1 integers has each value in 1..n with exactly one value repeated. Return the duplicate without modifying the array and in O(1) space.

Implement

find_duplicate(nums: list[int]) → int

Examples

in[[1,3,4,2,2]]out2

What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Learn the concepts

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.