#heap

35 heap interview questions, asked at Amazon, Google, Airbnb and 15 more companies. Last asked Sep 2026.

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Greedy and beam search decoding for a language modelCodingYou are writing the decoding step for a language model. Decoding turns the model's per-step scores into a sequence of token ids. Implement greedydecode(scores: listlistfloat) -…
Last asked Sep 2026
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GPU credit ledger with out-of-order eventsCodingBuild an in-memory ledger for GPU credits. Credit arrives as grants: each one has a unique id, an amount, and a time window in which it can be spent. Grants may overlap in time…
Last asked Sep 2026
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Task manager with user quotas and expiring assignmentsCodingBuild an in-memory TaskManager in four levels. Each level adds methods to the same class, and you move to the next level only after the current one passes. Every method takes an…
Last asked Sep 2026
Weighted cache that evicts the heaviest entriesCodingImplement WeightedCache, a key-value cache with a total-weight budget instead of an item count. Each entry has a positive integer weight. After every put, the sum of the weights…
Last asked Sep 2026
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Banking system with transfers, cashback and account mergesCodingBuild an in-memory banking system in four levels. Each level adds methods, and every earlier method must keep working. Every call takes a timestamp in milliseconds as its first…
Last asked Sep 2026
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Merge ordered streamsCodingMerge several ordered input streams into one ordered output without loading any stream fully into memory. Reported on 1point3acres' Sierra bank; reconstructed in our own words.
Last asked Sep 2026
Sort an array with k worker threadsCodingImplement parallelsort(nums: listint, k: int) - listint, which returns every element of nums in ascending order and uses k worker threads for the heavy lifting. Rules - Split nums…
Last asked Sep 2026
Sliding window average excluding the k largestCodingImplement windowedaverages(nums, windowsize, k). Slide a window of windowsize consecutive elements across the integer array nums, from left to right. For each full window, drop…
Last asked Sep 2026
Smallest valid task order from dependenciesCodingThere are n tasks numbered 0 to n - 1, done one at a time, and a list of pairs a, b meaning a must finish before b starts. Return an order that respects every dependency; among…
Last asked Aug 2026
Rearrange a string so no neighbours matchCodingGiven a string s of lowercase English letters, rearrange its characters so that no two adjacent characters are equal. Every character of s must be used exactly once. Implement: 1…
Last asked Aug 2026
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Top k largest elementsCodingGiven an integer array nums and an integer k, return the k largest elements of nums. You may return them in any order. The result is a multiset. If a value appears several times…
Last asked Aug 2026
Build a weighted binary tree from character countsCodingGiven a string s of letters ('A'-'Z', 'a'-'z'; case matters), build a binary tree that summarizes how often each character appears. Each node has three fields: ch, count, and two…
Last asked Jun 2026
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Live top-k best-selling books leaderboardCodingA bookstore wants a live leaderboard of its best-selling books. Sales arrive one at a time, and the leaderboard can be read at any moment. Implement a BookSalesTracker class: -…
Last asked May 2026
Meeting rooms: find conflicts and the minimum rooms neededCodingYou get room requests as half-open intervals start, end). First decide whether a single room can serve all of them (no two overlap). If not, return the fewest rooms needed so…
Last asked Feb 2026
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K-th greatest value in every growing prefixCodingYou are given arr, a permutation of the integers 1 to n (each value appears exactly once), and an integer k with 1 <= k <= n. Read arr from left to right. After reading each…
Last asked Feb 2026
Score an array by taking the smallest and marking its neighboursCodingStart with every element of an array unmarked and a score of 0. Repeatedly pick the smallest unmarked value (the leftmost one on a tie), add it to the score, and mark it together…
Last asked Jan 2026
Least-loaded task assignment with worker specialtiesCodingTasks arrive in a fixed order and must be handed out to a team of workers so that the work stays balanced. Each task has a unique integer id, a positive integer duration, and (in…
Last asked Jan 2026
Top k lottery winners by spendingCodingGiven lottery entries that record who bought tickets and how much they spent, return the top k people ranked by total spending. Discuss ties and how you would keep the answer…
Last asked Jan 2026
Autocomplete with top-k suggestionsCodingGiven a list of past queries with their counts, build an autocomplete: for a prefix the user has typed, return the k most popular completions. Use a trie, and discuss storing top…
Last asked Sep 2025
Real-time top-k products from purchase eventsCodingPurchase events (customerid, itemid, timestamp) arrive continuously. Keep a structure that returns the k most purchased items at any moment. Discuss the cost of updates and…
Last asked Sep 2025
Cache with expiry, priority and LRU evictionCodingImplement a fixed-capacity key-value cache, PriorityExpiryLRUCache. Every item stores a value, an integer priority, and an expiry time. When a new key arrives and the cache is…
Last asked Aug 2025
Most tasks finished before their deadlinesCodingGiven tasks with durations and deadlines, run them one at a time and choose as many as possible so that each finishes by its deadline. Return how many. Sort by deadline and use a…
Last asked Aug 2025
Maximum sum of a length-k subarrayCodingUse a sliding window to find the largest sum of any contiguous subarray of length k, and explain its time and space. The same round followed with a heap problem.
Last asked Aug 2025
Top-k clicked items over a rolling windowCodingClick events arrive with timestamps. Keep the k most clicked items over the last fixed window of time, evicting old clicks as time moves on. Follow-ups asked about optimizing it…
Last asked Jul 2025
Cheapest way to make product sizes distinctCodingProducts have sizes sizei, and raising product i's size by one costs costi. Sizes may only grow. Return the least total cost to make all sizes distinct. The same screen also had a…
Last asked Jul 2025
Music player that plays the most frequent unplayed songCodingUsers keep arriving, each with a list of songs, and every song's count goes up each time it appears. The player must always play the most frequent song that has not been played…
Last asked Mar 2025
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Minimum workers with first-free job assignmentCodingJobs arrive as (jobid, start, end) with half-open times start, end). Workers are numbered 0, 1, 2, ... Part 1. Process jobs by start time (ties by job id). Each job goes to the…
Disk block writes with limited write cyclesCodingA storage device has n blocks with ids 0 to n - 1. Every block can be written at most maxcycles times; after that it is worn out and can never be written again. Implement a…
Rearrange house numbers into sorted, duplicate-free neighborhoodsCodingA city is a list of neighborhoods. Each neighborhood is a list of house numbers (integers), and numbers may repeat, both within a neighborhood and across the city. Move houses…
Maximum profit from unit-time tasks with deadlinesCodingYou are given a list of tasks. Each task is a list of three strings: name, deadline, profit. - Every task takes exactly 1 second, and only one task can run at a time. - Time…
Maximum combination health of AI modulesCodingA lab is assembling an AI system from n candidate modules. Module i has a health healthi (how much it contributes) and a stability stabilityi (how reliable it is). Both are…
Maximize minus signs with positive prefix sumsCodingYou are given a list of positive integers nums = a1, a2, ..., an. Put a sign, + or -, in front of each number. Keep the order. After each position i, the running total of the…
Pick the highest-scoring movie row by top-k similarityCodingA user just finished a movie they liked. Your recommender already scored every other title for how similar it is to that movie, and the catalog is split into curated groups (rows…
Gift delivery scheduler with limited agentsCodingYou are planning gift deliveries to employees in an office. The workday runs from hour 9 to hour 17. You get: - intervals, a list of start, end pairs with integer hours. Employee…
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Median of a large unsorted array in linear timeCodingYou are given a very large, unsorted list of integers nums. Return its median. - If len(nums) is odd, the median is the middle value once the list is sorted. - If len(nums) is…