Longest Palindromic Substring: which companies ask it and how to practise

Longest Palindromic Substring is a Medium problem that 74 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 Palindromic Substring?

Public company lists attribute Longest Palindromic Substring, a Medium problem, to 74 companies. The most frequent askers are HPE, Nielsen and Cisco. 15 reports are from the last six months. It mainly tests two pointers, string and dynamic programming. Use this as a practice guide, not a promise.

Practise this kind of question aloud

Who asks Longest Palindromic Substring

74 companies appear in the public lists for this question. By how often each is reported: HPE (very often), Nielsen (very often), Cisco (very often), Tinkoff (very often), HSBC (very often), PhonePe (very often), ZS Associates (very often), DP world (very often), Disney (very often) and Wix (very often), and 64 more. 15 of them were reported in the last six months, Tinkoff, tcs and Microsoft 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 Palindromic Substring 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.

Two pointers walk a sorted or symmetric structure from both ends, or one fast and one slow. The proof that you never skip the answer is what the interviewer is waiting for.

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.

Dynamic programming is solving a problem from the answers to smaller copies of itself. Start with the plain recursion, find the repeated states, then store them; explain what the state means before you write any table.

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-palindromic-substring/ (opens the publisher's page). The statement is theirs; we do not reproduce it.

Questions to practise next

If you can solve Longest Palindromic Substring, try these next, chosen because they share its main topic and many of the same companies: Trapping Rain Water (Hard), Container With Most Water (Medium), 3Sum (Medium), Find Median from Data Stream (Hard), Move Zeroes (Easy) and Sort Colors (Medium). Each has its own page in the questions list.

Frequently asked questions

Is Longest Palindromic Substring asked at Amazon?

Amazon appears in the public lists for Longest Palindromic Substring, reported very often. Treat that as a reason to practise it, not a promise you will be asked it.

How hard is Longest Palindromic Substring?

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: