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TL;DR

Adversary Argument for Finding the Maximum: A canonical quantitative trading interview question at foundation difficulty. Commonly asked at Jane Street, HRT.

By Valenke Exam Prep Team·Last updated 2026-06-01
foundationComplexity & Lower Bounds

Adversary Argument for Finding the Maximum

Asked at: Jane Street, HRT

Problem
Prove that finding the maximum of nn distinct numbers requires at least n1n - 1 comparisons in the worst case. Then prove that finding both the maximum AND minimum simultaneously can be done in 3n/22\lceil 3n/2 \rceil - 2 comparisons.

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