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Derive max distinct frequencies for n items

Last updated: Mar 29, 2026

Quick Overview

The question evaluates combinatorial reasoning, discrete mathematics, and constructive extremal analysis by asking for the maximum number of distinct frequency counts in an array and a matching construction.

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  • Meta
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  • Software Engineer

Derive max distinct frequencies for n items

Company: Meta

Role: Software Engineer

Category: Statistics & Math

Difficulty: medium

Interview Round: Technical Screen

For an array of length n (n ≥ 1) with arbitrary integer values, what is the maximum possible number of distinct frequency counts among its distinct values? Derive a tight expression in terms of n and prove optimality. Discuss constructive examples that achieve the bound.

Quick Answer: The question evaluates combinatorial reasoning, discrete mathematics, and constructive extremal analysis by asking for the maximum number of distinct frequency counts in an array and a matching construction.

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Meta
Sep 6, 2025, 12:00 AM
Software Engineer
Technical Screen
Statistics & Math
3
0

Maximum Number of Distinct Frequency Counts in an Array

Context

You are given an array of length n ≥ 1 whose elements are arbitrary integers (values may repeat). For each distinct value, compute its frequency (number of occurrences). Among these frequencies, some values may coincide. We ask:

  • What is the maximum possible number of distinct frequency values that can appear?
  • Give a tight expression in terms of n, prove it is optimal, and present constructions that achieve the bound.

Task

  1. Define the function m_max(n): the maximum number of distinct frequency counts achievable by any length-n array.
  2. Derive a closed-form expression for m_max(n) in terms of n.
  3. Prove optimality (upper bound and matching construction).
  4. Provide small illustrative examples.

Solution

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