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Software Engineer Interview Questions
Practice 9403 coding, system design and machine learning questions from 546 companies, sorted by role, topic and interview round. Every question has step-by-step hints, a code runner that supports 8 languages and an AI mentor; members also get the full solution walkthrough.
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Showing 601–630 of 2629 results
- CircleMediumSoftware EngineerImplement a simplified multi-level banking system
Implement a simplified multi-level banking system evaluates algorithm design, data structures, correctness, complexity, edge cases, and implementation details in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Coding & AlgorithmsOnline Assessment - CircleMediumSoftware EngineerImplement cheapest itinerary with date filters
This question evaluates proficiency in graph algorithms and constrained pathfinding, including handling date filters for initial departures, time-ordered connections, cycle avoidance, and quantitative complexity analysis.
Coding & AlgorithmsOnline Assessment - CiscoHardSoftware EngineerImplement an LFU Cache
This problem tests your ability to design a data structure that supports O(1) insertions and lookups while managing cache eviction based on access frequency and recency.
Coding & AlgorithmsTechnical ScreenHash TableLinked ListDesign - CiscoEasySoftware EngineerLongest Substring Without Repeated Characters
This problem tests string manipulation, hash map usage, and the sliding window technique to find a specific substring based on unique character constraints.
Coding & AlgorithmsTechnical ScreenSliding WindowStringsHash Map - CiscoMediumSoftware EngineerSolve max-subarray, min-unique, and grid-jump
This question evaluates array algorithms and algorithmic problem-solving skills, specifically contiguous-sum optimization (greedy/DP reasoning), frequency counting and memory-constrained selection for unique minima, and grid traversal simulation with boundary and visit-state management.
Coding & AlgorithmsOnline Assessment - CitadelMediumSoftware EngineerCompute BBO and NBBO from order data
This question evaluates a candidate's skill in designing efficient data structures and algorithms for aggregating and querying order-book data, including computing best bid/ask prices and summing quantities at those prices.
Coding & AlgorithmsTechnical Screen - CitadelMediumSoftware EngineerCompute Every Fixed-Size Submatrix Sum
Compute every contiguous fixed-size submatrix sum without mutating the input, using a padded two-dimensional prefix grid to answer each window in constant time.
Coding & AlgorithmsOnsite - CitadelMediumSoftware EngineerCompute max team size with a core interval
This question evaluates algorithmic problem-solving around interval overlap and time-complexity optimization, measuring the ability to determine the maximum team size given a core interval while reasoning about interval intersections and scalability; it is commonly asked to assess correctness and subquadratic runtime thinking, categorized under Coding & Algorithms and emphasizing practical algorithmic implementation. The follow-up evaluates combinatorics and counting under adjacency constraints with modular arithmetic and efficient handling of large parameters, commonly posed to test recurrence reasoning and scalable counting approaches, falling under combinatorics/dynamic programming and emphasizing conceptual understanding linked to practical algorithmic efficiency.
Coding & AlgorithmsOnline Assessment - CitadelMediumSoftware EngineerCompute maximum later-earlier difference
This problem tests your ability to optimize an O(n^2) brute-force search into an O(n) linear-time solution using a single-pass scan while maintaining state variables.
Coding & AlgorithmsOnline AssessmentArraysOptimizationGreedy - CitadelMediumSoftware EngineerDesign a token manager with lazy expiration
This problem tests your ability to design a token management system that supports efficient retrieval, updates, and lazy removal of expired tokens using a combination of a hash map and a priority queue.
Coding & AlgorithmsTechnical ScreenHash MapHeapTTL - CitadelMediumSoftware EngineerDesign dynamic weighted random sampling with updates
This question evaluates a candidate's ability to design and analyze dynamic data structures that support weighted random sampling with inserts and deletes, testing skills in algorithm design, complexity analysis, and randomized sampling under large numeric constraints.
Coding & AlgorithmsOnsite - CitadelHardSoftware EngineerEvery MEX Reachable With At Most One Bounded Increment
A coding problem about memory blocks with values below n: using at most one increment of a single value, never raising a value to n, list every minimum excluded value (MEX) the array can end up with. It tests careful case analysis of how one increment can open or fill a gap, handling duplicate values, and returning the sorted answer efficiently.
Coding & AlgorithmsOnline Assessment - CitadelHardSoftware EngineerEvery Reachable Priority Gap After At Most One Bounded Bump
Given n network ports each tagged with a priority code below n, find every value the lowest unused priority code could take after at most one bounded increment. Tests careful case analysis of how a single bump opens or closes a gap, and returning the answer efficiently.
Coding & AlgorithmsOnline Assessmentarrayscountingmex - CitadelMediumSoftware EngineerFind earliest common meeting slot
This question evaluates proficiency with interval manipulation, timeline merging, and algorithmic reasoning for scheduling constraints, measuring competency in handling sorted interval lists, edge-case sanitization, and complexity analysis.
Coding & AlgorithmsTechnical Screen - CitadelMediumSoftware EngineerFind the Index Range of a Target in a Sorted Array
Implement an algorithm to find the first and last index of a target value in a sorted array in O(log n) time.
Coding & AlgorithmsTechnical Screenbinary-searcharrayscitadel - CitadelMediumSoftware EngineerFind the Shortest Target-Sum Path
This problem tests your ability to navigate binary trees using recursion or iterative traversal while maintaining state to find a path that meets a specific sum criteria with the smallest number of nodes.
Coding & AlgorithmsTechnical ScreenTreesDFSRecursion - CitadelHardSoftware EngineerFirst Free Locker Number After One Tag Bump
Given locker tags in [0, n-1], list every possible smallest missing tag after at most one capped +1 adjustment. Tests MEX reasoning, careful case analysis around duplicates, and an O(n) solution.
Coding & AlgorithmsOnline Assessmentarrayscountingcase-analysis - CitadelMediumSoftware EngineerGenerate Prefix-Based Product Suggestions
Generate up to three lexicographically smallest product suggestions for every prefix of a search word, with efficient handling once a prefix has no matches.
Coding & AlgorithmsOnsite - CitadelEasySoftware EngineerImplement LRU/LFU cache with custom eviction
This problem tests your ability to design a generic cache structure that supports interchangeable eviction strategies, requiring efficient lookup and metadata management.
Coding & AlgorithmsTechnical ScreenHash MapLinked ListCache - CitadelMediumSoftware EngineerImplement a single-producer multi-consumer ring buffer
This question evaluates understanding of ring-buffer data structures, circular indexing, fixed-capacity storage, and object-oriented design for a single-producer, multi-consumer implementation in C++.
Coding & AlgorithmsTechnical Screen - CitadelEasySoftware EngineerImplement an in-memory order book API
This problem tests your ability to design an in-memory data structure for an order book using efficient data structures to support order management and price-level aggregation.
Coding & AlgorithmsTechnical ScreenData StructuresHash MapTree - CitadelMediumSoftware EngineerImplement array merge, round-robin scheduler, and trading simulator
This problem tests your ability to manipulate data structures efficiently, implement a fair process scheduler, and manage event-driven state transitions.
Coding & AlgorithmsOnsiteArraysQueuesHeaps - CitadelMediumSoftware EngineerImplement task queue with insert, delete, execute
This question evaluates a candidate's ability to design and implement efficient dynamic priority management, including priority ordering, insertion-order tie-breaking, and support for add, remove, and execute operations.
Coding & AlgorithmsOnsite - CitadelMediumSoftware EngineerMaximize Earnings by Adding Working Days
Maximize schedule earnings by changing at most k days off into working days, balancing fixed daily pay with bonuses for consecutive working days.
Coding & AlgorithmsTechnical Screen - CitadelMediumSoftware EngineerMaximize Earnings by Converting Days Off
Tests dynamic programming and state tracking to maximize daily earnings and consecutive work streak bonuses under a budget of schedule changes.
Coding & AlgorithmsHR Screendynamic-programmingalgorithmssliding-window - CitadelMediumSoftware EngineerMerge K Drone Telemetry Streams Into a Running Altitude Timeline
Interleave K drones' individually time-ordered altitude logs into a single replay and track the fleet's shared altitude total as each logged change is applied. Tests k-way merging with a heap, a deterministic tie-break across drones, and correct handling of negative deltas and drones with no events.
Coding & AlgorithmsTechnical Screenheapmerge-intervalsstreaming - CitadelMediumSoftware EngineerMerge K Timestamp-Sorted Price Feeds into a Running Absolute Price
Merge K price-event feeds, each already sorted by timestamp, into one chronological stream and return the running absolute price after every event, starting from zero. It tests merging sorted sequences efficiently, a deterministic tie-break for equal timestamps by feed index and then in-feed order, negative deltas, empty feeds, and 64-bit accumulation.
Coding & AlgorithmsTechnical Screen - CitadelMediumSoftware EngineerMerge K timestamped lists with timestamp coalescing
This problem tests your ability to efficiently merge multiple sorted streams of data and aggregate values associated with the same timestamp.
Coding & AlgorithmsTechnical ScreenHeapMerge SortData Streams - CitadelMediumSoftware EngineerMinimize Changes to Make Every Password Block Palindromic
Tests string manipulation and two-pointer techniques to determine the minimum character replacements needed to make independent fixed-length blocks palindromic.
Coding & AlgorithmsHR Screenstringstwo-pointersgreedy - CitadelMediumSoftware EngineerMinimize changes for k-periodic palindrome
This question evaluates understanding of string algorithms and combinatorial reasoning, focusing on palindrome properties combined with k-periodicity and the ability to minimize character changes under global constraints.
Coding & AlgorithmsOnline Assessment
Circle
Citadel