Coding & Algorithms Interview Questions
Practice 3,013 real Coding & Algorithms interview questions for 2026. Coding & Algorithms interview questions for top tech firms like Meta, Amazon, Google, Uber, and TikTok — real questions from actual interviews with detailed solutions — to power your interview preparation. This collection is sharply focused on algorithmic patterns (arrays, strings, sliding windows, trees/graphs, dynamic programming, greedy, two-pointers, and hashing), clean, review-ready code, and the explanation skills that distinguish hires. In 2026 expect familiar medium-to-hard problems plus newer twists: AI-enabled or multi-file coding rounds at some companies, more emphasis on explainability and edge-case reasoning, and occasional real-world performance constraints (streaming, concurrency, memory limits). Interviewers evaluate problem framing, algorithm choice, complexity trade-offs, test-case thinking, and communication under time pressure. Best prep mixes pattern-based practice, timed mock interviews, code-review style polishing, and rehearsed explanations of complexity and tradeoffs. Focus your last-mile prep on writing correct, readable code quickly and on explaining why your solution is robust and efficient for production scenarios.
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Compute account balances with rejection and overdraft
You are given a list of transaction records as strings. Each record has the format: ` account_id,timestamp,currency,amount ` - account_id: string iden...
Find top co-viewed products
You are given a list of user browsing sessions, where each session is a list of product IDs, a target_product, and an integer k. A product should be c...
Compute max events in any 60-second window
Design a function that, given a non-decreasing list of integer timestamps (seconds), returns the maximum number of events occurring within any contigu...
Solve four algorithm design tasks
Solve the following four algorithmic tasks: 1) Implement wildcard pattern matcher: Given a text s and a pattern p where '?' matches any single charact...
Detect Trigger and Resolve Events
You are given transaction logs sorted by non-decreasing timestamp. Each log record has four fields: - timestamp: integer time in seconds - merchant_id...
Explain hash maps and solve array intersection
1) Explain the internal implementation of a hash map: underlying array/bucket layout, hash function choice, collision resolution strategies (separate ...
Solve four coding problems
The interview included four independent coding problems: 1. Longest all-healthy service streak You are given the daily health-check results for mul...
Solve meeting and tree problems
The interview included two coding tasks: 1. Merge meeting intervals You are given a list of meeting intervals [[start, end], ...], not necessarily ...
Solve Reported OA Coding Problems
The post describes several algorithm questions from an online assessment. The concrete problems that can be reconstructed are: 1. Remove Blocks in a G...
Build a Weekly Calendar
Implement an interactive weekly calendar UI. Requirements: - Display a one-week calendar with 7 days. - The calendar should be divided into 1-hour tim...
Implement Sparse Matrix Operations
Implement core sparse linear-algebra utilities for interview-style ML code. Tasks: 1. Compute the dot product of two sparse vectors efficiently. 2. Im...
Build Friend Recommendations
You are given a social graph and a User class that stores a user id and the set of direct friends for each user. Complete a recommendation module with...
Extend a Maze Solver
You are given an existing grid-based maze solver with bugs and several requested feature extensions. The maze uses the following symbols: - S: start -...
Evaluate variables in simple arithmetic DSL
You are given a small DSL (domain-specific language) consisting of variable assignments, one per line. Each line has the form: `text <identifier> = <e...
Design a circular queue data structure
Problem Design and implement a fixed-capacity circular queue that supports constant-time operations. A circular queue stores elements in an array of s...
Reorder Search Results for Provider Diversity
Build a function that paginates ordered provider listings for a telehealth marketplace. Each input record is a CSV string in the format: provider_id, ...
Implement Nested Transactional Key-Value Store
Implement an in-memory key-value store that processes a batch of commands, one command per line. The store must support nested transactions. Supported...
Generate the next lexicographic array arrangement
Question Given an integer array nums (which may include negative numbers and duplicates), modify nums in place to produce the next arrangement in lexi...
Implement several OA simulation problems
Reconstruct and solve the following coding problems from an online assessment. 1. Case-insensitive adjacent differences Given a string s, treat u...
Implement time-versioned KV store with restore
Design and implement an in-memory key–value store where every operation is associated with a timestamp (monotonically increasing integer). The store m...