#hash sets

6 hash sets interview questions, asked at Amazon, Google, Netflix. Last asked Aug 2026.

Track missing package IDs from out-of-order arrivalsCodingPackages with IDs 1, 2, 3, ... arrive in any order. Support recording an arrival, reporting the contiguous frontier (the largest ID such that every ID up to it has arrived), and…
Last asked Aug 2026
Deduplicate titles across a home page's visible rowsCodingA home page shows rows (shelves) of titles, and only the first few titles of each row are visible on the first screen. The same title may appear in several rows. Choose what to…
Last asked Jul 2026
Longest sequence whose neighbours differ by less than kCodingA variant of longest consecutive sequence: from the values in an array, find the longest sequence in which each neighbouring pair differs by less than k.
Last asked Apr 2026
Unique Morse code wordsCodingTranslate each word into Morse code by joining the codes of its letters, and return how many different translations there are.
Last asked Feb 2026
Fewest deletions so a list's first k items avoid another listCodingYou get two lists, a and b, and an integer k. Delete elements from b so that none of the first k elements of what remains also appears in a. Return the fewest deletions needed (or…
Last asked Feb 2026
Objects seen on both days by at least two clientsCodingTwo log files, one per day, hold lines of timestamp, objectid, clientid. Return the object ids that appear on both days and were accessed by at least two different clients. Then:…
Last asked Nov 2025