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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 211–240 of 781 results
- Capital OneMediumMachine Learning EngineerSolve Four Coding Assessment Tasks
This multi-part coding question evaluates array manipulation, algorithm simulation, deterministic spatial placement, and constrained optimization competencies across tasks involving cumulative thresholds, iterative subtraction sequences, fixed-shape grid placement, and minimal-increment adjustments for monotonic patterns.
Coding & AlgorithmsOnline Assessment - Capital OneEasyMachine Learning EngineerSolve OA tasks on string, grid path, subarrays
This problem tests proficiency in string manipulation, grid traversal with condition-based movement, and linear-time subarray analysis.
Coding & AlgorithmsOnline AssessmentArraysDynamic ProgrammingGrid Traversal - Capital OneMediumSoftware EngineerSolve four algorithmic coding tasks
This multi-part question evaluates algorithmic problem-solving across frequency counting (equal-value pairs), simulation and in-place grid transformation (match-three gravity), matrix diagonal pattern checking, and interval/range data-structure management, emphasizing correctness under constraints and rigorous time/space complexity reasoning.
Coding & AlgorithmsOnline Assessment - Capital OneHardSoftware EngineerSolve multiple algorithmic interview questions
This multi-part prompt evaluates algorithmic problem-solving and core data-structure competencies such as array manipulation, modular/date arithmetic, matrix transformations, dynamic set and interval maintenance, string concatenation frequency counting, and path-based expression evaluation on grids.
Coding & AlgorithmsOnline Assessment - Capital OneMediumSoftware EngineerSort Each Adjacent Pair of an Array, Leaving an Odd Last Element in Place
Given an integer array, put each consecutive pair of elements in ascending order while keeping every pair in its original place, and leave the final element untouched when the length is odd. Tests precise reading of a short specification and careful index handling.
Coding & AlgorithmsOnline Assessment - Capital OneMediumSoftware EngineerSort Every Concentric Matrix Border Clockwise
This problem tests array traversal, boundary management, and sorting logic by requiring you to isolate concentric layers of a matrix and sort their contents independently.
Coding & AlgorithmsOnline AssessmentArraysSortingMatrix - Capital OneMediumSoftware EngineerSorted Sums of Absolute Differences Over All Cyclic Shifts of an Array
Given two integer arrays of equal length, compute the sum of absolute differences between the second array and every cyclic rotation of the first, then return all of these sums in non-descending order. It tests rotation index arithmetic, accumulation over every shift, and exact output ordering.
Coding & AlgorithmsOnline Assessment - Capital OneHardSoftware EngineerSum of Distinct Values on the Borders of All Maximum-Sum Square Frames
Among all square frames of a given size inside an integer matrix, find those with the largest border sum, then add up the distinct values that appear on the borders of every such frame. Tests careful border enumeration that excludes interior cells, tie handling across several frames, and de-duplication by value.
Coding & AlgorithmsOnline Assessment - Capital OneHardMachine Learning EngineerSupport updates and count target-sum pairs
This problem tests the ability to maintain frequency counts of elements in a dynamic dataset and perform efficient range-sum queries for pairs that satisfy a target condition.
Coding & AlgorithmsOnline AssessmentHash MapData StructuresFrequency Array - Chicago Trading CompanyEasySoftware EngineerMerge Nested Dictionaries Iteratively
This question evaluates a candidate's skill in iterative data structure manipulation and handling of nested dictionary merging semantics, including conflict resolution and value overriding.
Coding & AlgorithmsOnline Assessment - CircleMediumSoftware EngineerDescribe pair-programming challenge under time pressure
Describe pair-programming challenge under time pressure evaluates behavioral evidence, ownership, communication, trade-offs, and measurable outcomes in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Behavioral & LeadershipOnline Assessment - CircleHardSoftware EngineerDesign banking payment scheduling system
This interview question evaluates requirements, scale assumptions, API/data design, architecture, trade-offs, failure modes, and rollout in a realistic interview setting. A strong answer for Design banking payment scheduling system states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
System DesignOnline Assessment - CircleHardSoftware EngineerDesign flight-price search service
Design flight-price search service evaluates requirements, scale assumptions, API/data design, architecture, trade-offs, failure modes, and rollout in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
System DesignOnline Assessment - CircleHardSoftware EngineerDesign in-memory DB with TTL and backup
A Circle software-engineer take-home: design a versioned in-memory key→(field→value) database with per-field TTL, append-only history and delete tombstones, lexicographically ordered scan and scanPrefix (correct even with special characters), and snapshot backup/restore counters. It exercises data modeling, time-travel visibility semantics, ordered indexing, garbage collection, and per-operation complexity trade-offs.
System DesignOnline Assessment - 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 - CircleMediumSoftware EngineerTrace and reduce redundant curl requests
A practical curl interview question on tracing and reducing redundant HTTP requests: instrumenting a curl-based client, finding duplicate calls, and cutting request volume. Includes a full worked solution.
System DesignOnline Assessment - CircleMediumSoftware EngineerWrite PostgreSQL updates with date filters
This question evaluates competency in PostgreSQL data manipulation, covering updates with correct timestamp handling, upserts with conflict resolution, date-range selection using timestamptz, and index design plus performance analysis with EXPLAIN ANALYZE.
Data Manipulation (SQL/Python)Online Assessment - 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 - CitadelHardData ScientistBuild a regression model for wind power output
This question evaluates competency in feature engineering, physics-informed regression modeling, sensor-data quality handling, model selection and validation, and uncertainty estimation for turbine-level instantaneous power prediction.
ML System DesignOnline Assessment - CitadelHardSoftware EngineerBuild models for housing and wind power prediction
This question evaluates ML system design and applied modeling competencies, including data assumptions, preprocessing, feature engineering, model selection, validation strategies, temporal leakage handling, and end-to-end pipeline construction for a binary housing-affordability classifier and a time-series regression for wind-farm power prediction.
ML System DesignOnline Assessment - 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 - CitadelHardData ScientistDesign a time-series home-buy decision classifier
This question evaluates competency in ML system design for time-series decisioning, including rigorous target and horizon definition, temporal feature engineering, time-aware validation, probabilistic calibration and thresholding, leakage controls, model selection trade-offs, and deployment monitoring.
ML System DesignOnline Assessment - 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 - 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 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 - CitadelMediumSoftware EngineerMinimize image processing cost with discount
This question evaluates a candidate's competence in algorithm design and optimization, including interval-based cost aggregation and modular arithmetic for large-number results within the Coding & Algorithms domain.
Coding & AlgorithmsOnline Assessment - CitadelMediumSoftware EngineerRefactor a Correct but Quadratic C++ Routine Under a Microsecond Budget
Optimize an inefficient, quadratic tree-resolution routine into a linear-time, cache-friendly implementation suitable for ultra-low-latency execution.
Software Engineering FundamentalsOnline AssessmentTreePerformance OptimizationGraph Traversal
Capital One
Circle
Citadel