Longest Substring Without Repeating Characters

Also reported as LeetCode 3

CodingAmazonLast reported September 2026Low Frequency

Reported: 3× across candidate reports
First seen: December 2025
Last reported: September 2026
Reported outcome: mixed

Problem Overview

The round: LeetCode 3, Longest Substring Without Repeating Characters, in three reports. An onsite in December 2025 opened with it as LeetCode problem 3; that candidate was not hired. An AWS new-grad onsite in September 2026 had two problems in a 30-minute coding slot, this one and Word Search II,…

1 candidate-reported follow-up — 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.

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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.