Coding questions

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1. Coding questions · xAI

   Per-Key Fixed-Window Cost Limiter with ALLOW and RESET Commands

   A coding problem about a cost-based rate limiter that processes ALLOW and RESET commands for many keys. Each key may spend a fixed budget per aligned time window and rejected requests record nothing, so it tests per-key window bookkeeping and 64-bit timestamp handling across up to 200,000 commands.

2. Coding questions · Citadel

   Perform EDA and diagnose data quality

   This question evaluates proficiency in exploratory data analysis and data quality assessment using pandas and related tools, covering inspection of data types, summary statistics, missing-value diagnostics, outlier detection, and feature correlation.

3. Coding questions · Uber

   Perform matrix Candy Crush elimination

   This question evaluates a candidate's competency in matrix and grid manipulation, neighborhood/adjacency checks, and simulation of state transitions in an array-based board.

4. Coding questions · Nuro

   Pick Two Trees for a Zipline That Maximizes Height Times Span

   A coding question that recasts the classic two-line container problem as choosing two trees in a row to string a zipline between. It asks for the largest value of the shorter tree's height times the distance between the two trees, over arrays of up to 100,000 heights, and tests efficient pair selection.

5. Coding questions · Intuit

   Pivot daily users and revenue by platform

   This question evaluates data manipulation and aggregation skills, specifically computing distinct user counts and revenue aggregates and reshaping results by platform; it is in the Data Manipulation (SQL/Python) domain and assesses practical application rather than purely conceptual understanding.

6. Coding questions · Instacart

   Pivot data without date libraries

   This question evaluates a candidate's competency in data manipulation and transformation, specifically pivoting tall datasets into wide views, handling missing metric values, ordering ISO date strings via string operations, and meeting algorithmic efficiency constraints (O(n log n)).

7. Coding questions · Instacart

   Pivot transactions by date without date libs

   This question evaluates proficiency in data manipulation, string-based date handling, aggregation and pivot transformations, along with reasoning about data structures, de-duplication and missing-value filling.

8. Coding questions · Amazon

   Place items into earliest fitting bins

   This interview question evaluates algorithm design, data structures, correctness, complexity, edge cases, and implementation details in a realistic interview setting. A strong answer for Place items into earliest fitting bins states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

9. Coding questions · ByteDance

   Place Non-Attacking Queens

   This question evaluates a candidate's competency in combinatorial search, constraint reasoning, and algorithmic design for arranging non-attacking pieces on a grid.

10. Coding questions · Stripe

    Plan bicycle routes on a city map

    This question evaluates graph algorithms and pathfinding competencies, multi-criteria optimization and weighting, data structure selection, heuristic design, handling dynamic updates and closures, and correctness and edge-case reasoning for route planning.

11. Coding questions · Fanatics

    Plot ASCII chart for time-price pairs

    This question evaluates skills in array manipulation, coordinate mapping, and ASCII-based data visualization, focusing on transforming unsorted time-price pairs into a fixed 2D grid and handling point collisions and empty cells.

12. Coding questions · Cockroach Labs

    Point-in-Time Reads from a Timestamped Key-Value Store

    Build a versioned key-value store whose reads return the value a key held at a given timestamp: the latest write at or before that time, or an empty string if there is none. Tests choosing a per-key data layout that keeps point-in-time lookups fast across up to 200,000 operations.

13. Coding questions · Microsoft

    Populate next pointers in a perfect binary tree

    Evaluates proficiency in tree traversal and in-place pointer manipulation, emphasizing the perfect binary tree invariant and space-time trade-offs; category/domain: Coding & Algorithms. It is commonly asked because it tests ability to perform level-wise linking under an O(1) extra-space constraint and operates at the implementation-level of algorithms and data structures.

14. Coding questions · Meta

    Posts and Replies Engagement

    This question tests practical SQL skills, specifically the use of LEFT JOIN and aggregate functions to compute engagement metrics across relational tables. It evaluates a data scientist's ability to handle zero-count rows and filter results using set-based logic, competencies commonly assessed in data manipulation interviews.

15. Coding questions · Voleon

    Pre-process Financial Data for Linear Regression Modeling

    This question evaluates data preprocessing and feature engineering skills—handling missing values, winsorizing outliers, standardizing predictors, and assembling X/y datasets using Python/Pandas within the Data Manipulation (SQL/Python) domain.

16. Coding questions · Faire

    Print a Centered Pascal Triangle

    This question evaluates the ability to generate combinatorial structures (Pascal's triangle) and apply precise numeric formatting, alignment, and string-layout skills, reflecting algorithmic thinking and attention to presentation details.

17. Coding questions · Uber

    Print directory tree with indentation

    This question evaluates proficiency with representing and traversing hierarchical directory trees and producing depth-based formatted output, testing concepts such as tree traversal, recursion or iterative depth tracking, and string formatting for indentation.

18. Coding questions · ByteDance

    Probability That One Fair Die Beats Another

    Solve a coding interview problem about the probability that one fair die beats another when the dice may have different sizes and duplicate face values. The challenge emphasizes strict tie handling and an efficient approach that avoids comparing every possible pair of faces.

19. Coding questions · DRW

    Process CSV for portfolio returns and metrics

    This question evaluates a candidate's competency in time-series data manipulation, financial return computation, portfolio analytics, numerical stability, modular software design (clear function boundaries and unit tests), and algorithmic complexity analysis within the Data Manipulation (SQL/Python) domain.

20. Coding questions · Meta

    Produce asymmetric side views of a binary tree

    Produce asymmetric side views of a binary tree 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.

21. Coding questions · Meta

    Produce dating profile funnel report by cohort

    This question evaluates a data scientist's competency in cohort-based funnel analysis, metric computation (counts and rates), temporal cohorting, deduplication, and aggregation of relational event and profile data.

22. Coding questions · Snowflake

    Propagate Permission Letters Through a DAG Using Each Node's Final State

    Given a directed acyclic graph in which each node grants and revokes letter permissions, compute every node's final set of letters when each node passes only its final state to its children. Tests topological processing, set propagation over multiple parents, and letters that descendants grant again after an ancestor revokes them.

23. Coding questions · LendingClub

    Query Active Loans by Borrower ID in SQL

    This question evaluates proficiency with SQL data aggregation, grouping, and ordering to compute borrower-level loan totals, assessing practical skills in relational data manipulation within the Data Manipulation (SQL/Python) domain.

24. Coding questions · Lyft

    Query and transform marketplace data in SQL/Python

    This question evaluates mastery of data manipulation and analytics skills in the Data Manipulation (SQL/Python) domain, including SQL aggregation and window functions, time-based joins and grouping, deduplication of status streams, handling late-arriving events, and implementing rolling metrics using both SQL and pandas.