Longest Common Prefix: which companies ask it and how to practise

Longest Common Prefix is a Easy problem that 52 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 Common Prefix?

Public company lists attribute Longest Common Prefix, a Easy problem, to 52 companies. The most frequent askers are Disney, Revolut and USAA. 12 reports are from the last six months. It mainly tests string and trie. Use this as a practice guide, not a promise.

Practise this kind of question aloud

Who asks Longest Common Prefix

52 companies appear in the public lists for this question. By how often each is reported: Disney (very often), Revolut (very often), USAA (very often), CME Group (very often), Yelp (very often), persistent systems (very often), Target (very often), oyo (very often), Wipro (very often) and SAP (very often), and 42 more. 12 of them were reported in the last six months, USAA, opentext and Bloomberg 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 Common Prefix tests

It is rated Easy, so interviewers expect a correct, complete solution and a clear statement of the time and space cost, often in the first 15 to 20 minutes, with time left for a variation.

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 trie stores strings by shared prefixes, so prefix queries cost the length of the prefix. Say the memory cost.

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

Questions to practise next

If you can solve Longest Common Prefix, try these next, chosen because they share its main topic and many of the same companies: Valid Parentheses (Easy), Longest Substring Without Repeating Characters (Medium), Group Anagrams (Medium), Longest Palindromic Substring (Medium), Decode String (Medium) and Valid Anagram (Easy). Each has its own page in the questions list.

Frequently asked questions

Is Longest Common Prefix asked at Amazon?

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

How hard is Longest Common Prefix?