Coding questions

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1. Coding questions · Freddie Mac

   Assess SQL cleaning, mapping, joins, keys, and DDL/DML

   This question evaluates skills in data cleaning, deduplication, schema mapping, referential integrity, DDL/DML, and SQL/Python data manipulation, focusing on joins, keys, validation of values, and ETL mapping competencies.

2. Coding questions · Fannie Mae

   Assess SQL joins, unions, windows, dedup, and pandas

   This question evaluates proficiency in SQL and pandas data-manipulation techniques, including aggregations with NULL semantics, various join types, set operations and deduplication, window functions, and reconciling normalized and denormalized sources.

3. Coding questions · eBay

   Assign Ads to Browser Positions

   This question evaluates algorithmic problem-solving around randomized selection, constraint-based resource allocation, and per-user state management, including enforcing eligibility rules and incrementing display counts.

4. Coding questions · ByteDance

   Assign Meetings and Find the Most-Used Room

   Practice an interval-scheduling problem where meetings may be delayed and room-number tie rules affect the final count. The prompt tests precise simulation, large-input complexity, integer safety, and careful handling of simultaneous room availability.

5. Coding questions · Whatnot

   Assign Waiting Riders to the Earliest-Arriving Car on Fixed Routes

   Cars drive fixed routes over a road map with travel times while riders wait at attractions for a ride to a destination. Assign each rider to the car that reaches their stop first while still visiting their destination later, break ties by car index, and list every car's riders. It tests route timing, indexing and tie handling.

6. Coding questions · Expedia

   Audit and onboard unfamiliar datasets safely

   This question evaluates a data scientist's competency in dataset discovery, schema and key verification, profiling for distributions/missingness/timezones/currencies, duplicate and join-inflation detection, event-sequence validation, accurate metric computation, and the design of data-quality tests/data contracts within SQL/Python workflows.

7. Coding questions · Capital One

   Audit flight data quality from metadata

   This question evaluates data quality auditing competencies, including validation of timestamps and timezones, detection of label leakage and inconsistent units, provenance and schema enforcement, and hands‑on use of SQL/Python for dataset inspection.

8. Coding questions · Waymo

   Average of a List of Integers, Returning 0 for an Empty List

   Write a function that returns the arithmetic mean of a list of integers and returns 0 for an empty list. A warm-up from a timed data science assessment that tests careful handling of the empty case and floating-point division.

9. Coding questions · Hudson

   Ball Position in a Tilting Maze After Timed Tilt Events

   Live coding simulation problem: a ball sits in a grid maze on a board that can tilt up, down, left or right or lie flat, and timed events change the tilt. Return the ball's cell at an end time that can be very large. It tests precise timing rules, wall handling and movement code that scales to long time spans.

10. Coding questions · Siemens

    Batch and Pad Variable-Length Vectors with Optional Final-Batch Dropping

    Build an ordered vector data pipeline with batch-local right padding, empty-vector handling, and optional dropping of the final incomplete batch.

11. Coding questions · Rippling

    Bill Deliveries with Historical Rates and Deferred Rounding

    Bill deliveries with start-time historical rates, duplicate suppression, overlapping jobs, exact sub-cent accumulation, and configurable final half-up or half-even rounding.

12. Coding questions · Capital One

    Block-Building Operations: Check Whether a Free Segment Starts at a Position

    Process operations on a number line that either place a block at a position or ask whether a segment of a given length starting at a position is free of blocks, and return the answers as a string of ones and zeros. It tests handling interleaved updates and range checks efficiently over large coordinates.

13. Coding questions · Amazon

    Build a BFS Web Crawler

    This question evaluates understanding of breadth-first traversal, URL normalization, domain scoping, duplicate detection, and retry/error handling, measuring algorithmic design and robustness in networked code.

14. Coding questions · Snowflake

    Build a cohort dashboard with Streamlit and SQL

    This question evaluates proficiency in cohort analysis using SQL window functions, time-based aggregation, ARPU calculation, and integration of data querying with a Streamlit visualization front end, including handling timezones and data-quality checks.

15. Coding questions · XPeng

    Build a Least-Recently-Used Store

    This question evaluates understanding of caching and eviction policies and practical proficiency with data structures such as hash tables and ordered collections for tracking and updating recency.

16. Coding questions · Sigmacomputing

    Build a Pivot Table Aggregator

    This question evaluates a candidate's ability to implement data aggregation and efficient lookup structures, focusing on grouping, associative aggregations, and maintaining intermediate state for derived metrics.

17. Coding questions · Uber

    Build a Quadtree and Analyze a Graph

    This question evaluates skills in spatial data structures and recursive tree construction (building a quadtree) as well as graph analysis using traversal and cycle/safety detection to identify nodes that necessarily reach terminal nodes.

18. Coding questions · Uber

    Build a QuadTree From a Grid

    This question evaluates understanding of spatial data structures and recursive divide-and-conquer techniques by compressing uniform regions into a QuadTree representation.

19. Coding questions · Snowflake

    Build a Top-Down Reporting Forest from Employee-Manager Pairs

    Given employee-to-manager pairs of integer IDs, build the top-down reporting forest with every top-level manager as a root, and return it as a preorder listing of IDs and depths. Tests finding the roots, building child lists, deterministic sibling ordering, and handling long reporting chains.

20. Coding questions · Square

    Build a Trust-Aware BIN Database

    Build an in-memory card-prefix database that resolves brand and card type independently across overlapping writes. Practice combining longest-prefix matching with trust and recency rules while preserving omitted fields and supporting heavy lookup traffic.

21. Coding questions · ByteDance

    Build a validated add-sub calculator

    This question evaluates skills in string parsing, tokenization, input validation, and safe integer arithmetic handling, with emphasis on enforcing format rules such as operator placement, prevention of leading zeros, and 32-bit signed integer bounds.

22. Coding questions · Chicago Trading Company

    Build an Ordered Latest-Quote Container

    Build an insertion-ordered container that stores only the latest quote for each stock symbol. Support expected O(1) push, pop, and size operations while updating bid and ask values without changing a symbol's original position and safely rejecting malformed commands.

23. Coding questions · Amazon

    Build DiD dataset with SQL

    This question evaluates proficiency in SQL-based data manipulation and panel construction for staggered-adoption difference-in-differences, testing skills in handling adoption dates, event-time calculations, boundary conditions, and aggregation in the Data Manipulation (SQL/Python) domain.

24. Coding questions · Nextdoor

    Build Ranked Feed With Photo Batching

    This question evaluates algorithmic reasoning and data manipulation skills, including stable sorting, grouping/batching, and merging of ranked items while preserving ordering invariants.