Coding questions

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1. Coding questions · Uber

   Implement three interview-style coding tasks

   This set of tasks evaluates algorithm and data-structure design skills within the Coding & Algorithms domain, focusing on array windowing and range constraints, dynamic connectivity with component-size maintenance, and time-windowed streaming counters with per-user rate limiting.

2. Coding questions · Perplexity

   Implement time-versioned KV store with restore

   This question evaluates a candidate's ability to design and implement a time-versioned key–value store, assessing knowledge of temporal data structures, versioning semantics, time-travel and range queries, deletion semantics, and rollback/restoration.

3. Coding questions · Netflix

   Implement topological sort from string input

   This question evaluates a candidate's skills in parsing unstructured dependency strings into directed graphs, producing a valid topological order, detecting and reporting minimal cycles, and reasoning about robustness against duplicate, unknown, or malformed inputs as well as time and space complexity.

4. Coding questions · OpenAI

   Implement toy-language types and generic substitution

   This question evaluates understanding of type systems, AST-style type representations, and generic type variable resolution by requiring implementation of Node and Function models and substitution of generics to infer concrete return types.

5. Coding questions · Square

   Implement transaction network queries

   This question evaluates the ability to model and query dynamic graph connectivity and reachability for pairwise transactions, testing competencies in graph representation, dynamic data structures, and reachability queries within the Coding & Algorithms domain and emphasizing practical application of algorithmic concepts.

6. Coding questions · Amazon

   Implement tree left/right views via BFS and DFS

   This question evaluates understanding of binary tree traversal techniques and algorithmic reasoning for producing per-depth left and right views, assessing competencies in data structures, traversal ordering, and correctness across edge cases.

7. Coding questions · SoFi

   Implement tree ops and LRU cache

   This question evaluates proficiency with tree-based mutable data structures and cache design, specifically maintaining aggregated state in a full binary tree after leaf updates and implementing an LRU cache supporting O(1) get/put operations.

8. Coding questions · Trexquant

   Implement Trie search with wildcard matching

   This question evaluates understanding of trie data structures, string pattern matching with wildcard characters, and efficient algorithm design for large-scale add/search operations.

9. Coding questions · Amazon

   Implement two array-cost minimization algorithms

   This question evaluates algorithm design, data structure selection, and complexity analysis by requiring implementations for minimizing total merge cost and for removing a contiguous block to minimize the sum of adjacent absolute differences.

10. Coding questions · xAI

    Implement two string utility functions

    This question evaluates proficiency in string manipulation and text processing, including character counting, tokenization by spaces, case-sensitive comparisons, and preserving original word order.

11. Coding questions · Uber

    Implement uniform sampling in squares

    Implement uniform sampling in squares 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.

12. Coding questions · Motive

    Implement Union-Find and track components

    This question evaluates understanding and implementation of the Disjoint Set Union (Union-Find) data structure, covering union by rank, path compression, API design for union(a, b), connected(a, b), count(), and analysis of time and space complexity.

13. Coding questions · Motive

    Implement Union-Find for connectivity

    This question evaluates understanding and implementation of the Disjoint Set Union (Union-Find) data structure—including path compression and union by rank—and competency in processing online connectivity queries on undirected graphs, categorized under Coding & Algorithms in the graph algorithms and data structures domain.

14. Coding questions · Netflix

    Implement weighted-eviction cache

    This question evaluates understanding and practical implementation of data structures and algorithms for a weighted cache, including weighted eviction policies, use of ordered maps, and time-space complexity analysis.

15. Coding questions · Meta

    Implement weighted random city and sparse dot product

    This pair of problems evaluates proficiency in randomized algorithms and numerical scalability for weighted sampling and in sparse linear algebra for computing dot products, testing competencies in data structures, algorithmic complexity, and handling large numeric ranges within the Coding & Algorithms domain relevant to machine learning engineering; the required level combines practical implementation detail with conceptual reasoning about numerical stability and performance trade-offs. They are commonly asked in technical interviews to gauge the ability to design time- and memory-efficient solutions for high-dimensional or high-volume data, reason about overflow and sparsity implications, and consider reuse or incremental updates to avoid redundant computation.

16. Coding questions · Uber

    Implement weighted sampling without replacement

    This question evaluates a candidate's ability to design numerically stable, streaming weighted-sampling methods and tests competencies in randomized algorithms, probability, numerical analysis, and memory/time trade-offs.

17. Coding questions · Hudson River Trading

    Implement Wordle-style word guessing solver

    Implement Wordle-style word guessing solver 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.

18. Coding questions · Meta

    Improve YoY Revenue Analysis with Complementary Metrics

    This question evaluates a data scientist's competency in time-series data manipulation and metric validation, focusing on calculating Year-over-Year advertising revenue with SQL/Python and window functions while recognizing pitfalls associated with rolling sums.

19. Coding questions · Capital One

    Impute, join, and upsert using SQL and Python

    This question evaluates SQL and pandas proficiency in data manipulation tasks including missing-value imputation, tiered aggregation, joins and upsert/deduplication, time-windowed revenue computation, cohort retention analysis, and handling of monetary versus non-monetary events within a relational schema.

20. Coding questions · Capital One

    Impute missing values without leakage

    This question evaluates proficiency in data imputation, strict train/validation leakage prevention, temporal per-user propagation rules, and categorical aggregation for model-ready features.

21. Coding questions · Patreon

    In-Memory Per-Second API Rate Limiter: Accept or Reject Each Request

    A coding question about an in-memory rate limiter that lets at most a fixed number of requests through per second. Given non-decreasing request timestamps in milliseconds, decide whether each request is accepted, testing exact one-second window boundaries, same-timestamp bursts, and the rule that rejected requests consume no capacity.

22. Coding questions · Waymo

    In-Place Rectangle Copy Within a 2D Array Using O(1) Extra Memory

    Copy a rectangular block of a 2D array to another position in the same array, in place with O(1) extra memory, where the source and destination blocks may overlap. Tests choosing a safe copy direction so that no value is overwritten before it is read.

23. Coding questions · Meta

    Infer an Unknown Alphabet Order

    This question evaluates a candidate's competency in graph-based reasoning, inference of ordering constraints from sequences of strings, and algorithmic manipulation of characters and relations.

24. Coding questions · Waymo

    Insert +, -, * and Parentheses Between Ordered Numbers to Reach a Target

    Given numbers in a fixed order and a target, insert +, - or * between them and add parentheses to reach the target, returning the lexicographically smallest fully parenthesized expression or an empty string. Starts with three numbers and generalizes to n, testing exhaustive search over expression trees.