combinatorics Interview Questions
28 interview questions in our bank cover combinatorics, most of them Coding & Leetcode-style Questions. They average 3.0/5 difficulty — medium — and each one was reported by a candidate after a real interview. Companies known to ask about combinatorics: Optiver, JPMorgan, BNY Mellon, SoFi, Google, and 15 more.
Practice these on the problems board →Companies that ask about combinatorics
Question mix
- Coding & Leetcode-style Questions28
Difficulty
- 2/5 — easy4
- 3/5 — medium19
- 4/5 — hard5
Questions tagged combinatorics
Stock Transaction Sequence Counting (Catalan / DP)
3/5Prepare for quantitative software engineering roles with this Optiver interview problem centered on tracking valid transaction sequences without falling into a negative balance. This challenge tests your grasp of advanced combinatorics, dynamic programming, and Catalan number applications common in market-making simulations. You must determine the exact count of admissible permutations under specific boundary rules efficiently. Unlock the detailed problem walkthrough and optimal code solution by purchasing a subscription.
Coding & Leetcode-style QuestionsOptiverCount Good Strings
3/5This Commvault interview question involves combinatorial counting and sequence validation under strict structural constraints. You must determine the total number of valid configurations of two distinct characters where prefixes maintain a specific balance condition, mirroring properties of well-formed parentheses or Dyck paths. The challenge evaluates advanced dynamic programming, combinatorics, and modular arithmetic skills. The complete problem details, mathematical derivation, and optimized code solution require a subscription.
Coding & Leetcode-style QuestionsCommvaultUnique Paths in a Grid
2/5Explore this classic grid traversal puzzle frequently featured in technical interviews at Amazon, where you must determine the total number of unique routes across a matrix from the top-left corner to the bottom-right destination. Movement is strictly restricted to rightward and downward steps, turning the challenge into an exercise in combinatorics or dynamic programming optimization. You will evaluate how to compute these configurations efficiently without redundantly recalculating sub-paths. Unlock the full problem breakdown, optimal algorithmic approaches, and clean reference code with a subscription.
Coding & Leetcode-style QuestionsAmazonDomino Tiling Recurrences (2xN and 3xN)
3/5Frequently featured in JPMorgan quantitative finance screenings, this problem explores combinatorial counting and mathematical induction through grid tiling scenarios. You will need to determine the number of ways to cover rectangular boards using smaller blocks, moving from standard two-row layouts to more complex multi-row variations. The core objective is to derive the underlying recurrence relations rather than simply memorizing numerical sequences. The full problem and model solution require a subscription.
Coding & Leetcode-style QuestionsJPMorganGenerate Random NFT (DFS + Weighted Sampling)
3/5This Coinbase interview question explores combinatorial generation and probabilistic sampling through the lens of creating unique digital collectibles with distinct attributes. Candidates must implement algorithms capable of systematically building combinations and handling weighted selections across multiple categorical traits. It tests deep understanding of recursive search strategies, tree traversal, and stochastic data handling. Discover the complete problem walkthrough and comprehensive source code by securing a paid subscription.
Coding & Leetcode-style QuestionsCoinbaseDigit Sum
3/5Encountered in a BNY Mellon interview, this problem revolves around a lottery system where participants hold numbered coupons and winners are determined by matching digit sums. You are tasked with finding the specific digital sum that maximizes the number of winning participants, as well as calculating how many alternative sums can achieve that exact maximum tie. The challenge tests your mathematical reasoning, digit manipulation, and frequency counting across a numerical range. Unlock the full prompt and complete model solution by purchasing a subscription.
Coding & Leetcode-style QuestionsBNY MellonCount Distinct Movement Subsequences on a Number Line
4/5This advanced algorithmic problem, frequently encountered in Visa technical screenings, explores counting valid directional sequences on a bounded integer track. Candidates must compute how many unique movement combinations successfully navigate from an origin to a destination without crossing boundary limits. The task thoroughly evaluates combinatorial logic, string processing, and dynamic programming or backtracking optimization. Unlocking the complete problem specification and its rigorous model solution requires an active subscription.
Coding & Leetcode-style QuestionsVisaAnagram Sentence Substitutions
3/5Featured in recent SoFi assessments, this challenge requires you to compute all possible sentence variations by substituting terms with their corresponding lexical equivalents. You will need to process a dictionary of letter-equivalent groups and evaluate how many permutations can be generated for a given set of statements. The task heavily emphasizes hash map aggregation and combinatorics. Unlock the complete problem guide and optimal solution by subscribing today.
Coding & Leetcode-style QuestionsSoFiEvery Length-3 Subsequence Has a Valid Permutation
3/5Investigate string combinatorics with this intricate Google interview question that examines the properties of subsequences against a predefined dictionary of valid words. You will need to evaluate whether every possible length-3 subsequence of a given text can be permuted to form a recognized vocabulary term. This task tests your combinatorial reasoning, pattern matching, and dictionary lookup strategies under complex constraints. Get full access to the complete problem description and model solution with a paid subscription.
Coding & Leetcode-style QuestionsGoogleCount Subarrays Where First = Last = Max
3/5Examine this intriguing array processing puzzle reported during technical rounds at LinkedIn. The objective is to identify and tally specific segments within a numeric sequence where the boundary values match the peak magnitude of that segment. Solving this efficiently demands a strong grasp of linear-time data structures, specifically utilizing monotonic stacks to maintain boundary relationships without brute-force scanning. Discover the detailed problem context and the optimal linear-time solution by getting a subscription.
Coding & Leetcode-style QuestionsLinkedInGenerate Parentheses
3/5Practice this popular interview question reported at Disney, where you must systematically construct all well-formed sequences of paired symbols for a given count. The objective is to generate combinations that adhere strictly to nesting rules and maintain proper balance from start to finish. This problem is excellent for building recursion and backtracking skills. The complete problem guide and reference solution require a active subscription.
Coding & Leetcode-style QuestionsDisneyCount Same-Bit Numbers
3/5This reported coding interview question from SoFi challenges candidates to explore bit manipulation and combinatorics. Given a positive integer, the objective is to count all numbers up to the next full-ones bitmask that share the exact same count of active binary bits, excluding the starting value itself. This task tests your ability to efficiently reason about binary representations and combinatorial limits without resorting to slow brute-force iterations. Access to the full problem description and complete model solution requires a subscription.
Coding & Leetcode-style QuestionsSoFiPaint Fence
3/5Tackle a combinatorial coloring puzzle frequently reported in technical screenings at Ripple, where you must determine the total number of valid permutations for decorating a sequence of items using a limited palette. The core objective is to avoid forbidden consecutive matches while satisfying strict boundary conditions. This problem evaluates your grasp of dynamic programming and recurrence relations to efficiently compute large combinatorial spaces. Unlock the complete breakdown and expert solution by subscribing today.
Coding & Leetcode-style QuestionsRippleQuant Probability and Statistics Orals
3/5Prepare for quantitative finance interviews with this JPMorgan oral statistics and probability challenge covering infinite nested radicals, combinatorics involving coupled pairs, and game-theoretic expected values. This evaluation tests your mathematical intuition, quick mental agility, and rigorous statistical reasoning under interview pressure. Access the complete set of oral questions and expert-crafted model solutions with a paid subscription.
Coding & Leetcode-style QuestionsJPMorganCounting Arrays
3/5Exploring combinatorial state spaces and numerical sequences is a common theme in algorithmic screening, exemplified by this Demonware interview challenge. Participants must determine the total quantity of distinct arrays that can be generated through iterative decrement operations on subsets of elements, ensuring results are appropriately bounded. This problem exercises deep combinatorial reasoning, pattern recognition, and efficient modulo arithmetic. Access to the complete problem text, detailed constraints, and expert solution is reserved for subscribed members.
Coding & Leetcode-style QuestionsDemonwareNon-Consecutive Process Allocation Counting (Modulo 1e9 + 7)
2/5This Citadel assessment problem asks you to calculate valid scheduling permutations across consecutive time slots with adjacency restrictions. It evaluates combinatorial reasoning and fast modular arithmetic techniques to handle large numerical outputs. You will formulate a recurrence relationship to efficiently count non-overlapping configurations. The full problem breakdown and optimal code implementation require a subscription to access.
Coding & Leetcode-style QuestionsCitadelCount Unique Paths in a Grid
3/5Determine all possible movement routes across a matrix from the top-left corner to the bottom-right destination in this classic Okta interview task. The challenge tests your dynamic programming and combinatorics knowledge by restricting movement to specific directions only. You must construct an efficient approach that scales well with grid dimensions while avoiding redundant computations. Access to the complete problem description, constraints, and optimized model solution requires a subscription.
Coding & Leetcode-style QuestionsOktaArray Break
4/5Featured in D. E. Shaw assessments, this coding problem requires you to split a numeric sequence into two parallel component arrays satisfying strict sorting constraints and split-sum equations. It evaluates your ability to combine dynamic programming or combinatorial counting with modulo arithmetic for large numerical outcomes. Unlocking the complete problem statement, comprehensive test cases, and the expert model solution requires a subscription.
Coding & Leetcode-style QuestionsD. E. ShawTrading OA — Probability Quickfire Closed Forms
3/5Sharpen your quantitative reasoning with this rapid-fire probability and expected value challenge reported from Citadel quantitative assessment processes. This set of questions explores combinatorial distributions, randomized shuffling outcomes, and uniform spatial separations, requiring sharp mathematical intuition and closed-form derivations under strict time constraints. It is an excellent test of fundamental stochastic concepts for quantitative roles. To review the complete question set and detailed mathematical solutions, a subscription is required.
Coding & Leetcode-style QuestionsCitadelSum of Compressed Number for All Subarrays
4/5Featured in coding evaluations at Wells Fargo, this advanced problem explores subarray compression and combinatorial counting. You are asked to analyze an integer array by collapsing consecutive duplicate elements and computing specific subsequence reduction metrics across all possible contiguous segments. This task tests deep combinatorial insight and efficient range query handling. Gain access to the full problem description, mathematical analysis, and optimal programmatic solution with a paid subscription.
Coding & Leetcode-style QuestionsWells FargoCount Subsequences
3/5Examine this advanced data processing challenge frequently reported in technical assessments at BNY Mellon, centered around analyzing numerical sequences for machine learning workflows. Candidates must compute specific subsequence properties within bounded ranges while applying modulo arithmetic to manage large numbers efficiently. Access to the full problem context and optimized algorithmic solution requires a subscription.
Coding & Leetcode-style QuestionsBNY MellonStock Prices
3/5This Rubrik interview question delves into array manipulation and combinatorics. You are given a sequence of daily stock prices and a divisor. The objective is to identify and count all unique combinations of three distinct days, where the sum of the stock prices on those days is perfectly divisible by the given divisor. This problem requires careful consideration of indices and efficient ways to iterate through combinations while applying modular arithmetic principles. It's an excellent test of your ability to handle numerical constraints and optimize for performance. The full problem and model solution require a subscription.
Coding & Leetcode-style QuestionsRubrikCount Square Subgrids For Each Query
2/5This Goldman Sachs interview question presents a combinatorial challenge involving grid geometry. For each given set of grid dimensions (rows and columns), your task is to determine the total number of square subgrids that can be formed within it, considering all possible side lengths. This problem requires a systematic approach to counting and an understanding of how the number of possible squares changes with increasing side length relative to the grid dimensions. It's a good test of your mathematical reasoning and ability to derive a general formula. The full problem and model solution require a subscription.
Coding & Leetcode-style QuestionsGoldman SachsNumber of Ways to Wear Different Hats to Each Other
4/5Tackle a sophisticated combinatorial matching challenge reported in Uber coding interviews that evaluates advanced algorithmic reasoning. You need to compute all distinct assignment permutations ensuring that multiple participants each receive a preferred item without any duplicates, constrained by categorical preferences. This puzzle tests your proficiency with backtracking strategies optimized via bitmasking and dynamic programming. Unlock the comprehensive walkthrough and verified code solution by becoming a subscriber.
Coding & Leetcode-style QuestionsUberStock Transaction Sequence Counting (Catalan / DP)
3/5This quantitative assessment problem, reported during recruitment rounds at Optiver, challenges candidates to count valid transaction sequences that maintain proper balance without dipping into negative totals. Relying on advanced combinatorics, counting principles, and dynamic programming techniques, this exercise tests your ability to model state transitions accurately. Access to the full problem description and its detailed model solution requires a paid subscription.
Coding & Leetcode-style QuestionsOptiverMorse Code Decoding — Count All Decodings
4/5Tackle an advanced combinatorial puzzle involving ambiguous translations of continuous dot-and-dash signals into valid alphabetic sequences, featured in technical rounds at Google. This problem assesses your proficiency in dynamic programming, recursive parsing, and string manipulation when handling inputs lacking explicit separators. You will learn to count all possible valid segmentations efficiently. The full problem statement, complexity analysis, and clean model solution require an active subscription.
Coding & Leetcode-style QuestionsGoogleProbability of a Dice Roll Sum
3/5This Belvedere Trading interview question challenges you to compute the likelihood of obtaining a specific aggregate outcome when throwing standard multi-sided dice multiple times. It evaluates your grasp of probability theory, combinatorics, and dynamic programming approaches for counting valid outcomes. To view the full problem statement and expert model solution, a subscription is required.
Coding & Leetcode-style QuestionsBelvedere TradingPrint Pascal's Triangle (Symmetric Formatting)
2/5Explore mathematical number generation paired with aesthetic output formatting in this engaging coding challenge reported from Faire interviews. The task evaluates your ability to construct numerical sequences based on additive rules while correctly aligning text elements for symmetric visual presentation. You will practice managing multi-dimensional row generation, spacing calculations, and clean console output formatting. Hone your implementation details and string alignment proficiency to ace similar structural coding rounds. The full problem and model solution require a subscription.
Coding & Leetcode-style QuestionsFaire
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combinatorics interview FAQ
- How many combinatorics interview questions are there?
- 28 reported questions, mostly Coding & Leetcode-style Questions.
- Which companies ask combinatorics questions?
- Optiver (2), JPMorgan (2), BNY Mellon (2), SoFi (2), Google (2), Citadel (2), Commvault (1), Amazon (1).
- How hard are combinatorics questions?
- They average 3.0 out of 5: 4 at 2/5, 19 at 3/5, 5 at 4/5.