#sorting

105 sorting interview questions, asked at Amazon, Google, Microsoft and 19 more companies. Last asked Oct 2026.

Sorting complexity: beat O(n²), then design the worst correct sortCodingA verbal round with no coding, asked as a quick series: 1. Explain a sorting algorithm faster than O(n²) and why it is faster; be ready for quicksort's worst case. 2. Name or…
Last asked Oct 2026
Best value from unit-weight items with limited copiesCodingA bag holds at most capacity units of weight. There are n kinds of item; every copy of kind i weighs 1 and is worth valuesi, and there are countsi copies of it. Return the most…
Last asked Oct 2026
Merge overlapping collinear segments in the planeCodingSegments in 2D each carry an ordered list of points. Merge segments that lie on the same line and overlap, keeping every point, and take care with vertical segments and…
Last asked Oct 2026
Sort an array with one misplaced elementCodingSort a nearly sorted array in which a single element sits out of place, faster than a full sort. Reported on 1point3acres' Glean bank; reconstructed in our own words.
Last asked Sep 2026
Rank transform of a matrix with distinct valuesCodingGiven an m x n matrix of distinct integers, replace each value with a rank starting at 1 so that in any row or column a larger value gets a larger rank, and ranks are as small as…
Last asked Sep 2026
+4
Maximum overlap of closed intervalsCodingGiven a list of closed intervals start, end (both endpoints included), return the largest number of intervals that contain one point on the number line. Two intervals that only…
Last asked Sep 2026
Three-card showdown between two playersCodingDesign a two-player card game that uses a standard 52-card deck. Each card has a rank and a suit. From lowest to highest, the ranks are 2 3 4 5 6 7 8 9 10 J Q K A. The suits are C…
Last asked Sep 2026
Hotel stay email schedule with booking changesCodingA hotel wants to send each guest a set of emails around their stay. Write the code that produces the full email schedule. Input - reservations: a list of objects with guestname…
Last asked Sep 2026
+1
Three sum: unique value triplesCodingReturn every unique triple of values from an integer array that sums to zero (or to a given target), with no duplicate triples in the output. Sort, then fix one value and move two…
Last asked Sep 2026
Sort a grid into snake order with adjacent swapsCodingAn n x n board holds each number from 1 to nn once. Rearrange it into snake order: the first row increases left to right, the second right to left, and so on, alternating. The…
Last asked Sep 2026
+2
Cloud storage with user quotas and backupsCodingDesign an in-memory cloud storage service. The interview has four parts. Each part adds methods, and every earlier method must keep working. Implement a class CloudStorage. File…
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
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
Median house price in each cityCodingGiven a list of house sales with a city and a price, return the median price for each city. Group the prices by city in a dictionary, sort each group, and take the middle value…
Last asked Sep 2026
Remove the fewest distinct values to delete half the arrayCodingPick a set of distinct values and delete every occurrence of each from an integer array. Return the smallest set size that removes at least half of the elements. Explain the…
Last asked Aug 2026
+1
Shuffle, deal and sort a four-player card handCodingYou are building the core of a four-player card game. Model a standard 52-card deck and implement the deal. Types to define - Suit: CLUBS, DIAMONDS, HEARTS, SPADES, in this order…
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
Highway toll checkpoints from plate logsCodingA highway has numbered toll checkpoints. Each checkpoint's name contains its position as a number, for example "A1" is at position 1 and "CP12" is at position 12. Ignore every…
Last asked Aug 2026
+5
Merge intervalsCodingGiven a list of intervals (for example time ranges), merge every group of overlapping intervals and return the result in sorted order.
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
Deduplicate and order logs from batch and streaming sourcesCodingLog records come both in batches and as a live stream; some are duplicates and some arrive out of order. Produce a single output that has each record once, in timestamp order…
Last asked Jul 2026
Sort a hundred million digitsCodingYou need to sort one hundred million single digits. How do you do it fast? Explain why a general comparison sort is the wrong tool here, what to use instead, and how memory and…
Last asked Jul 2026
+2
Vertical order traversal of a binary treeCodingGive every node of a binary tree a column (root at 0, left child one less, right child one more) and a row. Return the node values column by column from left to right, top to…
Last asked Jun 2026
Minimal unique word abbreviationsCodingGiven a list of distinct words, give every word the shortest abbreviation that no other word shares. An abbreviation keeps a prefix of the word, then the count of skipped letters…
Last asked Jun 2026
Sort clothing sizesCodingGiven a list of clothing sizes such as S, M, L, XS and XL, sort them from smallest to largest. Clarify which sizes can appear (for example, how many Xs may come before S or L) and…
Last asked Jun 2026
+1
Days when the whole team is freeCodingA team is planning an offsite over a window of numdays days, numbered from 1 to numdays. Each team member has entered busy blocks as triples (personid, startday, endday). Both…
Last asked Jun 2026
Kth largest perfect binary subtreeCodingIn a binary tree, find every subtree that is a perfect binary tree and return the size of the kth largest.
Last asked Jun 2026
Find conflicting eventsCodingGiven a list of events with start and end times, find the events that overlap one another.
Last asked Jun 2026
Shortest unique prefix for each wordCodingGiven a list of distinct words, return for each word its shortest unique prefix: the shortest leading substring of the word that no other word in the list starts with. Return the…
Last asked Jun 2026
Sort colors in placeCodingYou get an array of records, each tagged red, green or blue. Sort it in place so all reds come first, then greens, then blues, in one pass and constant extra space (the Dutch…
Last asked Jun 2026
Allocate inventory by bid priorityCodingAllocate a limited inventory across a set of bids, serving the bids in priority order, and report what each bid receives.
Last asked Jun 2026
+1
Employee shift timeline tableCodingEach shift is given as name, start, end, with integer times and start <= end. A shift covers the half-open interval start, end). One employee may have several shifts, and they may…
Last asked Jun 2026
Minimum triggers to clear linked balls on a gridCodingYou are given n balls on a 2D grid. ballsi = xi, yi is the position of ball i, and you are also given a non-negative integer d. Two balls are linked when they lie on the same row…
Last asked Jun 2026
Find the closest version by dateCodingGiven versions and their release dates, return the version whose date is closest to a query date.
Last asked Jun 2026
+3
In-memory SQL table with filtering and multi-key sortingCodingBuild a small in-memory SQL-like database. You do not need to parse SQL text. Queries arrive as structured arguments. Implement SQLManager: - createtable(name: str, columns:…
Last asked May 2026
Consolidate on-call rotation segmentsCodingAn on-call schedule is a list of segments, each naming a person and a start and end time. Merge the segments that belong to the same person and touch or overlap, and return the…
Last asked May 2026
Most common website visit patternCodingGiven which user visited which website and when, find the sequence of three websites that the most users visited in that order.
Last asked May 2026
Fewest points to pay across reward programsCodingA user holds points in several programs (airline miles, credit card points, store points). Each program has a balance and a dollar value per point that changes daily. To pay a…
Last asked May 2026
Refund allocation across prioritized payment methodsCodingA customer's order was paid with one or more payments, and some of them may already have been partly refunded. Implement a function that splits a new refund across those payments…
Last asked Apr 2026
+1
3SumCodingReturn every unique triple of values in an integer array that adds up to zero, with no duplicate triples in the answer. Aim for O(n^2) time after sorting.
Last asked Apr 2026
Sort colors (three-way partition in place)CodingAn array holds only three kinds of values, such as 0, 1 and 2. Sort it in place in one pass without a counting sort. Explain the Dutch national flag partition and its invariants.
Last asked Apr 2026
Factory network cost with stage-to-stage transportCodingA company is planning a chain of factories. Each factory has several candidate options, and you must pick exactly one option for every factory. The interview comes in parts; each…
Last asked Apr 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
Palindrome number and merge intervalsCodingTwo short problems: 1. Decide whether an integer reads the same forwards and backwards. 2. Merge a list of possibly overlapping ranges into the fewest non-overlapping ranges.
Last asked Mar 2026
Russian doll envelopesCodingEach envelope has a width and a height. One fits inside another when both its width and height are strictly smaller. Return the largest number of envelopes you can nest one inside…
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
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
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
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
+1
Meeting 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
Fewest boards to cover every hole in a roofCodingA roof has holes at given positions along a line, and boards of a fixed length can be laid over it. Return the fewest boards needed so every hole is covered. Sort the holes and…
Last asked Feb 2026
Zero out duplicates and sort an arrayCodingGiven an unsorted array of about 75 integers that may contain duplicates, replace the repeated copies with zero and return the array sorted. Discuss the time and space of your…
Last asked Feb 2026
+1
Closest latency pairs by minimum absolute differenceCodingA monitoring service records latency readings (whole milliseconds) and wants to flag readings that are suspiciously close to one another. Implement minabsdiffpairs(latencies:…
Last asked Feb 2026
Merge two sorted arrays in placeCodingTwo integer arrays, arr1 and arr2, are each sorted in ascending order. Merge arr2 into arr1 without using another array, so that arr1 ends up holding all the values, still…
Last asked Feb 2026
Most distinct values after shifting each element by at most kCodingYou may add any integer between -k and k to each element of an array, choosing independently for each. Return the largest number of distinct values the array can end up with.
Last asked Jan 2026
Card authorization report with fraud rulesCodingA payment platform receives authorization requests: a card holder's intent to pay a merchant. Write a function that decides each request and returns a report. Each request is a…
Last asked Jan 2026
Free 30-minute time slotsCodingGiven the busy intervals in a day, return every available 30-minute slot.
Last asked Jan 2026
H-index of instance ratingsCodingGiven the integer ratings of a set of instances, return the largest integer k such that at least k instances have a rating of k or more (return 0 when no such k exists). Do it…
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
Pair servers as primary and backup to maximize memoryCodingEach server has a memory size. Choose servers and group them into pairs, each pair a primary and a backup, where the backup must be able to take over for its primary (its memory…
Last asked Jan 2026
Recover the original array from its doubled shuffleCodingAn array was built by taking an original array, appending twice each of its values, and shuffling the result. Given the shuffled array, return the original, or an empty result if…
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
Most deliveries on a line within a distance limitCodingDelivery points lie on a number line and the courier may travel at most a given distance. Choose deliveries to complete as many as possible, and among the best choices, minimise…
Last asked Dec 2025
Party hours and quiet gaps by neighborhood and cityCodingA community events app records every party in two separate lists that share a partyId: - partyWindows: rows of partyId, start, end. start and end are hours as strings, and a party…
Last asked Dec 2025
Parking lot occupancy peaks from entry and exit eventsCodingYou get parking events carid, time, 'entry' 'exit', not necessarily in order. 1. What is the largest number of cars that were in the lot at the same time? 2. Return the time…
Last asked Dec 2025
Safe ranges between planets' gravity zonesCodingPlanets sit on a line; each is given as (center, radius) and makes the range within its radius unsafe. Return the safe ranges between the unsafe zones, in order. Turn each planet…
Last asked Nov 2025
Print timed text intervals in order and flag overlaps and gapsCodingYou get a list of time intervals, each with a piece of text, and print them in time order, much like merge intervals. The follow-up asks you to report where two intervals overlap…
Last asked Nov 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
Find the gaps between intervalsCodingGiven a list of intervals in any order, return every gap that no interval covers between the earliest start and the latest end. It is merge intervals, but you return the spaces in…
Last asked Nov 2025
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
Split tasks between two workers when one takes exactly kCodingThere are n tasks. Worker one earns reward1i for task i and worker two earns reward2i. Every task goes to exactly one worker, and worker one must do exactly k tasks. Return the…
Last asked Oct 2025
Sort characters by frequencyCodingGiven a string, rearrange it so the most frequent characters come first, each character's copies kept together. Count with a hash map, then sort or bucket by count.
Last asked Sep 2025
Unload warehouses in turns with limited skipsCodingYou and a co-worker empty warehouses one at a time; warehouse i holds ci items. You take turns: you remove m items per turn and your co-worker removes n. You earn a point for a…
Last asked Sep 2025
Earliest common slot in two calendarsCodingGiven two people's calendars as lists of time intervals and a meeting length, return the earliest slot of that length that works for both, or nothing. Clarify whether the…
Last asked Sep 2025
Sort strings by length, then merge two sorted listsCodingGiven two unsorted lists of strings, sort them by string length. Follow-up: if both lists already arrive sorted by length, merge them into one sorted list in linear time.
Last asked Sep 2025
Most distinct values of B[i] mod A[i]CodingYou get an array A of n positive integers. You choose any array B of length n, and compute Bi % Ai for every i. Return the largest possible number of distinct values among these…
Last asked Sep 2025
Most optional tasks under a daily time limitCodingEach day has the same time limit. Every day must run its required task; if time allows, it can also run one optional task. You get n required durations (one per day) and n…
Last asked Sep 2025
Order jumps between blocks to burn the most caloriesCodingYou stand on the ground (height 0) next to n blocks of given heights. You must jump onto every block exactly once, in any order, and you never return to the ground. A jump from…
Last asked Sep 2025
Shortest unsorted continuous subarrayCodingFind the shortest contiguous subarray that, if sorted, makes the whole array sorted, and return its length. Start from sorting a copy, then find an O(n) two-pointer solution.
Last asked Aug 2025
Car poolingCodingA vehicle with a given capacity drives in one direction. Each trip is passengers, start, end. Return whether all trips fit without ever exceeding capacity, by sorting pickup and…
Last asked Aug 2025
Most days picking distinct productsCodingYou have quantities of several products. On day i (starting at 1) you must pick exactly i items, each from a different product, out of what is left. Return the largest number of…
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
Largest and smallest median over length-k subsequencesCodingGiven an array and an integer k, consider every subsequence of length k and its median. Return the largest and the smallest of those medians.
Last asked Jul 2025
Rank vehicles by peer-to-peer update contributionCodingA fleet of electric vehicles receives over-the-air software updates split into fixed-size chunks. Chunks come from the distribution server over cellular data, which is expensive…
Last asked Jul 2025
Fewest intervals to remove so one covers the restCodingGiven a list of intervals, remove as few as possible so that among the remaining intervals at least one covers all the others. Return how many you remove.
Last asked Jul 2025
Remove items so any k prices stay under a thresholdCodingA store is planning a holiday promotion from a list of candidate items with known prices. Shoppers may pick any k items from whatever stays on the list, and the store wants every…
One-hot encode an integer arrayCodingWrite onehot(arr: listint) - listlistint that returns the one-hot encoding of an integer array as a 2D list. - The matrix has one row per element of arr, in the same order. - It…
Best single location on a line to minimize total distanceCodingYou are choosing one location on a number line to serve a set of sites. You are given a non-empty integer array nums. Each value is the coordinate of a site (values may repeat and…
+2
Fewest coins that cover every amount up to a limitCodingYou are given a list of coin denominations (positive integers) and an integer maxamount. You may take any number of coins of each denomination. Choose a multiset of coins so that…
+1
Shortest equal length for two boards covering every holeCodingA table top has holes at integer positions along a single line, given as an unsorted array holes (positions may repeat or be negative). You will patch it with exactly two boards…
Maximum tests in one activation windowCodingA shared test environment receives test cases over time. You are given an integer array arrivalTime, where each entry is the time one test case arrives. Several test cases can…
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 stability of a server groupCodingA cloud provider offers n servers. Server i has two positive integer scores: reliabilityi and availabilityi. A client deploys on any non-empty group of servers. A group is only as…
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 total cluster throughput from median-of-three serversCodingYou manage a fleet of host servers. hostThroughputi is the throughput of server i (a non-negative integer). Group servers into clusters of exactly three distinct servers. Build as…
Assign node labels to maximize the total edge sumCodingYou are given an undirected graph with n nodes numbered 0 to n - 1 and a list edges, where edgesi = a, b is an edge between nodes a and b. Give every node a label so that the…
Frequent user events within a 24-hour windowCodingYou are given a list of activity log entries. Each entry has a userid (string), a timestamp (integer seconds since epoch) and an eventtype (string). The list is not sorted…
Recent file tracker with date and insertion orderCodingImplement a FileStorageSystem class that records files and answers two kinds of listing queries. - storefile(file: str, date: str) - None records a file with its storage date…
Sort words by a custom alphabetCodingYou are given a string order that lists characters from first to last in a custom alphabet. Each character appears in order at most once. You are also given a list of strings…
Finish times for round-robin tasksCodingA single worker processes a list of tasks. Task i needs arri hours of work in total. The tasks wait in a queue in index order. Each turn, the worker takes the task at the front…
Take down servers in a reliability drill with minimum total requestsCodingA reliability drill shuts down a fleet of n servers. Server i handles requesti requests every second while it is up, and starts with healthi health. You are also given an integer…
ATM queue exit orderCodingThere are n people waiting in a single line at an ATM. They are numbered 1 to n from the front of the line to the back. You are given an integer array amounts, where amountsi is…
Match applicant skills and versions to a job's requirementsCodingAn applicant tracking system screens candidates by the skills they list. Each applicant gives one comma-separated string of skills, strongest first. A job posting gives a…