Key-value cache with per-entry TTLCodingImplement an in-memory key-value cache where every write gives a key, a value and a time-to-live. Once an entry's time is up it must behave as if it was never written. Support…
Last asked Oct 2026
#heaps
Median of several sorted arraysCodingYou get several integer arrays, each sorted in non-decreasing order. Return the median of all their values taken together. The interview started with exactly two arrays and then…Last asked Oct 2026
Fault-tolerant work queue with leases and retriesCodingImplement an in-memory work queue that keeps working when workers crash. Workers take a task, process it, and report success or failure. A worker that dies silently must not lose…Last asked Oct 2026
Top-k prefix suggestions filtered by departmentCodingA service has a fixed list of suggestions, each (ngram, department, score). Implement getTopSuggestions(query, userDept, k), returning the k best-scoring suggestions that match…Last asked Sep 2026- Rotating title picker for a home-page billboardCodingBuild a component that picks which title to show next in a billboard (or plays next in a playlist). Every title has a relevance score, and scores can change at any time. Each call…Last asked Sep 2026
- Lexicographically smallest topological orderCodingGiven tasks and the dependencies between them, return an order that runs every task after the tasks it depends on. When several tasks are ready at once, always pick the smallest…Last asked Sep 2026
Merge sorted arrays, then sort files too large for memoryCoding1. Merge two sorted arrays of integers into one sorted array. 2. The two inputs are now huge files that don't fit in memory. Merge them with bounded memory and buffered reads and…Last asked Sep 2026- Most active user by distinct contacts, then top KCodingUsers send each other messages, and a message between A and B counts as contact for both of them. Build a class with: - register(a, b): record a message between a and b. -…Last asked Sep 2026
Minimum buses to run a timetableCodingA bus depot has a timetable of trips, each with a departure time and an arrival time. A bus can take a new trip once it has arrived from its previous one. Return the fewest buses…Last asked Sep 2026
+5Top K frequent elementsCodingGiven an integer array and k, return the k values that occur most often, in any order; ties at the cutoff may go either way. One version asks for the most frequent request IDs in…Last asked Sep 2026
+1Find the median from a data streamCodingNumbers arrive one at a time; after any of them, return the median of everything seen so far. Keep two heaps (a max-heap for the lower half and a min-heap for the upper half)…Last asked Sep 2026- Min-priority queue without a library heapCodingImplement a min-priority queue yourself, without a library heap: insert, look at the minimum, and remove the minimum. Give the cost of each operation.Last asked Aug 2026
- Kth largest element in a streamCodingValues arrive one by one. After each value, return the kth largest value seen so far. It was framed as a product catalog that must report its top items.Last asked Aug 2026
Meeting rooms II: fewest rooms for a set of meetingsCodingGiven meetings as start, end) intervals, find the fewest rooms needed so that no two overlapping meetings share a room, and assign each meeting to a room.Last asked Aug 2026- K closest points to a query locationCodingGiven a list of 2D points and a query location, return the k points closest to it by Euclidean distance. Compare sorting, a size-k max-heap and quickselect, and say which you…Last asked Aug 2026
- Fewest rental cars for a set of reservationsCodingEach rental reservation has a start time and an end time. Find the fewest cars that can serve every reservation, and assign each reservation to a car. Follow-ups from other…Last asked Aug 2026
- Reusable locker allocation systemCodingBuild a system that hands out lockers and takes them back so they can be used again: assign a free locker on request, release it later, and keep both operations fast as the number…Last asked Aug 2026
- Meeting rooms: attend all, rooms needed, busiest roomCodingGiven meetings as start and end times: 1. Can one person attend every meeting? 2. What is the fewest rooms needed to hold all of them? 3. With a fixed number of rooms and a rule…Last asked Aug 2026
- Debug a Python job schedulerCodingYou own a small in-process job scheduler. It runs on a fake clock so it can be tested. Users report that: - a nightly report scheduled for exactly the end of a window sometimes…Last asked Jul 2026
- Schedule tasks with cooldownsCodingTasks of several types run one per time unit, and two tasks of the same type must be separated by a cooldown. Arrange the tasks so the rule holds and the total time (idle slots…Last asked Jul 2026
Alien dictionary with the smallest valid orderCodingYou get a list of words (password hints) that is sorted under an unknown alphabet. Work out an order of the characters that is consistent with that sorting, and when several…Last asked Jun 2026- Most frequent IP addresses in a file too big for memoryCodingA log file of IP addresses is far larger than memory. Find the most frequent address, then the top K. Explain how you split the work into pieces that fit in memory, count each…Last asked Jun 2026
- Priority task executor with duplicate task idsCodingImplement an executor that accepts tasks, each with an id and a priority, and runs them highest priority first. The same task id can be submitted more than once. Decide and…Last asked Jun 2026
Task scheduler that pops the earliest deadline once its subtasks are doneCodingImplement a class with addtasks(tasks) and consumetask(). Each task has an id, a deadline and a list of subtasks. 1. consumetask returns the task with the earliest deadline, or a…Last asked May 2026- Busiest meeting room after simulated bookingsCodingSimulate booking meetings into a fixed set of rooms and return the room that held the most meetings. Agree on the rules first: which free room a meeting takes, and what happens to…Last asked Mar 2026
- Top K largest distinct valuesCodingGiven an array that may contain repeats, return the k largest distinct values.Last asked Mar 2026
- Ads retrieval service using a heapCodingBuild a service that returns the best ads for a request, ranked by score, using a heap. Support adding and removing ads, and discuss the cost of each operation.Last asked Mar 2026
Merge k sorted listsCodingMerge k sorted linked lists into one sorted list. Compare a min-heap of list heads with pairwise merging, and give the time complexity in terms of the total number of nodes and k.Last asked Feb 2026- Kth largest element in an arrayCodingReturn the k-th largest element of an unsorted array. Compare sorting, a size-k min-heap and quickselect, with their time and space costs.Last asked Feb 2026
+1Single-threaded scheduler for one-shot, delayed and periodic tasksCodingBuild a scheduler that runs on a single thread and accepts three kinds of jobs: run once now, run once after a delay, and run every N units of time. Decide how the clock moves…Last asked Feb 2026- Minimum servers for daily jobs that wrap past midnightCodingEach job runs every day over a time window on a 24-hour clock, and a window may wrap past midnight (start later than end). A server runs one job at a time. Return the fewest…Last asked Feb 2026
- +1Meeting rooms IICodingGiven meeting start and end times, return the fewest rooms needed so no two overlapping meetings share a room, with a min-heap of end times or by sweeping sorted starts and ends.Last asked Feb 2026
- Top K frequent elements and K closest pointsCodingTwo warm-up style problems that the interviewer combined into one round: 1. Return the k points closest to the origin. 2. Return the k most frequent values in a list. Then combine…Last asked Feb 2026
Trapping rain water IICodingGiven a 2D grid of cell heights, compute how much rainwater the grid holds after rain, with water able to run off the outer edge.Last asked Feb 2026
K-th largest value over the last N seconds of a streamCodingStart with finding the k-th largest element of an array. Then values arrive with timestamps and queries ask for the k-th largest among values from the last N seconds; design a…Last asked Jan 2026- Top-k and bottom-k words in a list and in a streamCoding1. Given a list of words, return the k most frequent and the k least frequent. 2. Now the words arrive as a stream: keep both answers available at any moment. 3. Discuss how to…Last asked Jan 2026
- K largest subset sumsCodingYou get n items with non-negative weights. Return the k largest subset sums, in decreasing order (subsets are distinct by the items they contain). Brute force over all subsets is…Last asked Jan 2026
- Meeting rooms with delayed starts: the busiest roomCodingThere are n rooms numbered from 0 and a list of meetings with distinct start times. Each meeting takes the free room with the lowest number; if none is free, it waits for the…Last asked Jan 2026
- Logger that reports its top K messagesCodingBuild a logger that receives messages over time and can return the k most frequent messages at any point. Choose structures so logging stays fast and the top-K query is efficient…Last asked Jan 2026
- +2Find K pairs with the smallest sumsCodingGiven two sorted arrays and k, return the k pairs (one number from each array) with the smallest sums. Start a min-heap with pairs formed from the first elements and push the next…Last asked Dec 2025
- Top K similar movies from a similarity graphCodingMovies are nodes with a rating, and an edge links two similar movies; similarity carries across edges. Given a movie and k, return the k highest-rated movies reachable from it…Last asked Dec 2025
- Running median of a streamCodingNumbers arrive one at a time; after each, report the median of everything seen so far. Use two heaps. Follow-ups: the values come from a small range (use counts instead of heaps);…Last asked Dec 2025
- Load balancer with worker states, a priority queue and autoscalingCodingIn a time-boxed backend round, write a small load balancer in Python. Workers move through states (for example starting, idle, busy, draining), requests go to workers through a…Last asked Dec 2025
- The skyline problemCodingBuildings are given as left, right, height rectangles on flat ground. Return the outline of the skyline they form, as the list of key points where the height changes. Use a sweep…Last asked Dec 2025
- Report timed-out simulations from start, ping and end eventsCodingSimulations send start, ping and end events with timestamps. After each new event, return the simulations whose last activity is now older than the timeout and that have not ended.Last asked Dec 2025
- Many timers on top of one underlying timerCodingThe system offers a single timer: setting it replaces any earlier setting, and it calls a handler when it expires. Build a class that supports many independent timers on top of…Last asked Dec 2025
- Top three categories by total scoreCodingYou get a list of (category, score) tuples. Add up the score of each category and return the best total you can get from at most three categories (the three highest totals)…Last asked Dec 2025
- Top K most active users from chat logsCodingYou get chat log lines, each naming the users involved. Return the k users who took part in the most chats. Count with a hash map, then compare picking the top k by sorting, by a…Last asked Dec 2025
- Employee free timeCodingYou get each employee's busy schedule as a sorted list of non-overlapping intervals. Return the finite intervals in which every employee is free, in sorted order. Merge the busy…Last asked Nov 2025
Merge k sorted arraysCodingMerge several sorted arrays into one sorted array with a min-heap holding one element from each array. Give the O(N log k) cost and compare with pairwise merging.Last asked Oct 2025- K closest points to the originCodingGiven points in the plane and k, return the k points nearest to the origin in any order. Start simple (sort by distance), then improve with a size-k max-heap or quickselect and…Last asked Oct 2025
- Kth smallest element in a sorted matrixCodingEvery row and every column of an n x n matrix is sorted ascending. Return the k-th smallest value. Compare a min-heap over the rows with binary search on the value range.Last asked Sep 2025
- Top three scores for each studentCodingGiven records of student ID and score, return each student's three highest scores. Group by student and keep the top three with a small heap; when you learn that scores are whole…Last asked Aug 2025
- Log manager that evicts the least important logsCodingDesign a log manager that keeps at most totalmax logs. Each log has an importance; when a new log would go over the limit, the least important logs are deleted automatically…Last asked Aug 2025
- Sliding window medianCodingGiven an array and a window size k, return the median of every window as it slides one step at a time. Keep two heaps (or a sorted container) and remove elements leaving the…Last asked Jul 2025
- Task scheduler with a cooldown between identical tasksCodingGiven a list of tasks (letters) and a cooldown n, identical tasks must be at least n time units apart; the CPU can idle. Return the fewest time units to run them all. Solve it…Last asked Jul 2025
- Max stackCodingDesign a stack that also supports peekMax() and popMax() (removing the top-most copy of the largest value), along with push, pop and top. Compare a two-stack design with a doubly…Last asked Jul 2025
- Check whether a binary tree is a max-heapCodingDecide whether a binary tree is a valid max-heap: it must be complete (checked level by level) and every node must be at least as large as its children.Last asked Jul 2025
- Maximize capital with K projects (IPO)CodingYou start with some capital and may complete at most k projects. Each project needs a minimum capital to start and adds a profit when done. Pick projects to end with the most…Last asked Jul 2025