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Top K Frequent Elements at Stripe — Interview Guide

How to approach Top K Frequent Elements in a Stripe interview: the optimal approach, what Stripe interviewers look for, and company-specific tips.

Updated 2026-09MediumHeaps & Hashing

The problem at Stripe

Given a non-empty array and an integer k, return the k most frequent elements. The answer is guaranteed unique.

Stripe uses this problem to assess apis, money, and pragmatic engineering. Expect Stripe-specific follow-ups that tie the solution back to production reasoning and the company's engineering bar.

Key concepts

Count frequencies with a hash map in O(n).
A min-heap of size k keeps the top k by frequency in O(n log k).
Bucket sort by frequency achieves O(n) when values are bounded.

Approach

import heapq, collections
def top_k(nums, k):
    freq = collections.Counter(nums)
    return heapq.nlargest(k, freq.keys(), key=freq.get)

What Stripe looks for

Pragmatic engineering — code that works and is maintainable.
API and product thinking — design interfaces developers love.
User empathy — Stripe cares deeply about developer experience.
Clarity in writing and communication.

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