Longest Substring Without Repeating Characters: which companies ask it and how to practise

Longest Substring Without Repeating Characters is a Medium problem that 97 companies are reported to ask. This page shows who, how often and how recently, what the question tests, and how to practise it out loud with an interviewer who asks follow-ups. We link to the original problem statement instead of copying it.

Which companies ask Longest Substring Without Repeating Characters?

Public company lists attribute Longest Substring Without Repeating Characters, a Medium problem, to 97 companies. The most frequent askers are FreshWorks, Netskope and Turing. 27 reports are from the last six months. It mainly tests hash table, string and sliding window. Use this as a practice guide, not a promise.

Practise this kind of question aloud

Who asks Longest Substring Without Repeating Characters

97 companies appear in the public lists for this question. By how often each is reported: FreshWorks (very often), Netskope (very often), Turing (very often), Walmart Labs (very often), Wissen Technology (very often), Zoho (very often), ServiceNow (very often), EPAM Systems (very often), Visa (very often) and Yelp (very often), and 87 more. 27 of them were reported in the last six months, Turing, Wissen Technology and Zoho among them.

These are candidate reports collected in public lists, not statements from the companies. They are a good guide to what to practise and a poor guide to what you will be asked: interviewers change questions, and the same company asks different questions by team and level. Last reviewed 25 October 2026.

What Longest Substring Without Repeating Characters tests

It is rated Medium, which is the level most interviews are built around: expect to talk through two approaches, pick one, code it cleanly, and answer a cross-question on an edge case or a change to the constraints.

A hash table trades memory for speed: remembering what you have seen turns a repeated search into a lookup. Interviewers want you to say that trade-off and the cost of collisions or a bad key.

String problems test careful index handling and knowing which characters you may assume. Say out loud whether the input is ASCII, whether case matters, and what an empty string should return.

A sliding window keeps a running answer for a moving range. Say what makes the window valid and when you shrink it.

How to practise it

Do not just solve it silently. In a real interview you explain the approach before you code, write while you talk, and defend the solution to follow-ups. Set a timer, say the brute force and its cost first, then improve it, and finish by stating the time and space complexity and two edge cases you tested.

On giveinterview you can take this kind of question as a spoken interview: the AI interviewer opens with the problem, watches you code, asks cross-questions and ends with a scorecard. Your first 3 single-question interviews are free for life, every interview report is free, and a new account also gets 6 welcome credits.

Read the original statement here: https://leetcode.com/problems/longest-substring-without-repeating-characters/ (opens the publisher's page). The statement is theirs; we do not reproduce it.

Questions to practise next

If you can solve Longest Substring Without Repeating Characters, try these next, chosen because they share its main topic and many of the same companies: Two Sum (Easy), LRU Cache (Medium), Group Anagrams (Medium), Top K Frequent Elements (Medium), Subarray Sum Equals K (Medium) and Longest Consecutive Sequence (Medium). Each has its own page in the questions list.

Frequently asked questions

Is Longest Substring Without Repeating Characters asked at Amazon?

Amazon appears in the public lists for Longest Substring Without Repeating Characters, reported very often. Treat that as a reason to practise it, not a promise you will be asked it.

How hard is Longest Substring Without Repeating Characters?

Do I need to memorise the solution?

No. Interviewers listen for how you reason: the approach, the trade-offs, the edge cases and the complexity. Practise explaining it, not reciting it.

Sources and review date

Last reviewed 25 October 2026 Statements about other products come from their own public pages: