Autocomplete / Prefix Search with Frequency and Timestamp

CodingRobloxLast reported December 2025Medium Frequency

Reported: 4× across candidate reports
First seen: May 2025
Last reported: December 2025
Reported outcome: mixed

Problem Overview

Given three arrays — queries (strings), timestamps (integers, one per query), and prefixes (strings) — for each prefix find all matching queries (queries that start with that prefix), then output them sorted by frequency (descending). If two queries appear the same number of times, break ties by the minimum timestamp…

4 candidate-reported follow-ups — the exact probes interviewers asked, with the trigger for each
The rest of the problem statement — full requirements, constraints, and edge cases
Approach and trade-offs — what passing candidates did, and the mistakes that sink people

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Verified Source

Every question is reconstructed from multiple independent candidate reports. Verbatim follow-ups, not invented ones.

Codex Fact-Checked

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Interviewer Follow-ups

The exact follow-ups reported by candidates, with the trigger that prompts each one — plus the mistakes that sink people.