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Coding questions
Explore algorithm tutorials, coding and system design questions, interview experiences, and computer science study guides.
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Coding questions · Roblox
Track Highest-Earning Experience
This question evaluates the ability to maintain and query aggregated state with frequent updates, focusing on data structures for efficient real-time tracking of maximum values and dynamic key-value aggregations in the coding and algorithms domain.
Coding questions · Applied Intuition
Track simulations and report timeouts
This question evaluates competency in algorithms and data-structure design for real-time stream processing, including maintaining per-simulation state, handling time-based expirations, and reasoning about performance and correctness.
Coding questions · Ramp
Track Users From Flight History
This question evaluates competency in processing and aggregating temporal event data, including time-interval reasoning, counting/grouping per user, and designing efficient data structures and algorithms for large datasets.
Coding questions
Track Workers, Sessions, Promotions, and Bonus Pay
Implement worker sessions, current metadata, promotions, ordered filtering, and time-clipped compensation with historical rates and non-stacking double-pay intervals.
Coding questions · OneMain Financial
Transform clickstream with pandas sessionization
This question evaluates proficiency in time-series data manipulation, sessionization logic, timestamp imputation, robust ordering of out-of-order events, and scalable chunked processing using pandas or SQL-based techniques.
Coding questions · Uber
Transform DataFrame and compute diff-in-diff
This question evaluates proficiency in data cleaning (type conversion), missing-data handling, group-period aggregation, and estimating treatment effects via difference-in-differences.
Coding questions · Amazon
Transform event logs with subscription windows in pandas
This question evaluates a candidate's competency in time-based event attribution and temporal interval manipulation using pandas, covering interval merging, subscription-aligned revenue aggregation, anomaly flagging, and handling edge cases like overlapping or back-to-back subscriptions.
Coding questions · Boston Consulting Group
Transform messy transactions with pandas
This question evaluates proficiency in large-scale data manipulation and feature engineering using pandas, covering timestamp normalization across time zones, deduplication and last-write-wins semantics, data validation, memory-efficient aggregation, rolling-window statistics, and top-k categorical extraction for merchant categories.
Coding questions · Pinterest
Transform nested dicts with pandas apply/lambda
This question evaluates proficiency in pandas-based data manipulation, including flattening nested list and dict structures, parsing nested attributes, computing per-user aggregates and segment metrics, and implementing robust, vectorized extraction logic that handles missing keys and avoids SettingWithCopy pitfalls.
Coding questions · Amazon
Transform retail data with pandas groupby/merge/concat
This question evaluates pandas-based data manipulation skills, specifically proficiency with groupby/agg, merge/concat, rolling-window and time-series aggregations, deduplication and tie-breaking logic for ranking and joins.
Coding questions · Snowflake
Transform tree with subtree sum mapping
Transform tree with subtree sum mapping 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 questions · LinkedIn
Traverse a Binary Tree in Zigzag Level Order
Return binary-tree values level by level while alternating left-to-right and right-to-left order without changing level membership.
Coding questions · Microsoft
Traverse a Matrix in Clockwise Spiral Order
Traverse a rectangular matrix in clockwise spiral order without modifying the input. Learn the four-boundary technique and the guards that prevent duplicate visits on the final row or column.
Coding questions · Pinduoduo
Traverse a Matrix in Spiral Order
Traverse a rectangular matrix in clockwise spiral order using shrinking boundaries. Handle empty, single-row, and single-column inputs without duplicates while achieving linear time and constant auxiliary space beyond the result.
Coding questions · Microsoft
Traverse an Org Chart by Level
This question evaluates understanding of tree and graph data structures, transforming flat employee-manager relations into a hierarchical org chart, level-order traversal, and reasoning about data integrity issues such as cycles, missing managers, or multiple roots.
Coding questions · Meta
Traverse levels selecting nodes meeting a predicate
Traverse levels selecting nodes meeting a predicate 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 questions · Fannie Mae
Understand SQL Aggregations and Joins: Key Differences Explained
This question evaluates a candidate's competency in SQL aggregations (COUNT, SUM, AVG, MIN, MAX), join semantics (INNER, LEFT, RIGHT, FULL OUTER), set operations (UNION vs UNION ALL), window functions, view versus table trade-offs, duplicate detection and removal, query optimization techniques, and pandas DataFrame operations (merge, join, concat) within the Data Manipulation (SQL/Python) domain. It is commonly asked because it assesses both conceptual understanding (function purposes and join semantics) and practical application (writing efficient queries, deduplicating data, and translating patterns between SQL and pandas), thereby probing correctness and performance reasoning.
Coding questions · Amazon
Understand SQL: DELETE vs TRUNCATE, VIEW vs TABLE, CROSS JOIN
This question evaluates a candidate's understanding of core SQL concepts and data-manipulation competencies, covering the behavior of data-deletion operations, distinctions between logical and physical data structures, and join semantics.
Coding questions · Boston Consulting Group
Unify 7 tables and impute missing values
This question evaluates data-wrangling and ETL competencies including normalization of inconsistent schemas, performant joins, aggregation, and hierarchical imputation strategies in pandas, as well as handling of missing values and final schema validation.
Coding questions · Apple
Unit Ratio Queries Across Independent Unit Families with Modular Answers
A graph coding problem: given multiplicative conversion factors between units that split into independent families, answer queries for how many units of one unit equal one unit of another, returning the ratio modulo a prime or -1 when the units cannot be converted. It tests graph traversal over a forest and modular arithmetic.
Coding questions · Indeed
Unrolled Linked List with Insertion-Point Splitting
Implement unrolled-list get and insert with the exact insertion-point split rule, global indices, observable block snapshots, and honest complexity bounds.
Coding questions · Yahoo
Use OrderedDict to dedupe stably
This question evaluates a candidate's ability to implement stable deduplication using Python's ordered mapping types while handling case-insensitive comparisons that preserve original casing, and to reason about algorithmic complexity such as O(n) time and O(k) space.
Coding questions · Amazon
Validate 9x9 grid in one pass
This interview question evaluates algorithm design, data structures, correctness, complexity, edge cases, and implementation details in a realistic interview setting. A strong answer for Validate 9x9 grid in one pass states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Coding questions · ByteDance
Validate a bracket string
This question evaluates understanding of stack data structures, string parsing, and matching logic for balanced brackets and parentheses. It is commonly asked in technical interviews within the Coding & Algorithms domain to assess the ability to produce correct and efficient bracket-matching logic, testing practical application of data-structure implementation alongside conceptual understanding of stack behavior and edge-case handling.