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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"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."
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Explain coding solution and alternatives
Explain the logic behind your solution to a previous coding problem (e.g., the second coding task in this interview). Walk through your approach step ...
Design a versioned key-value store
Design and implement a versioned key-value store that supports set(key, value, timestamp) and get(key, timestamp) to retrieve the most recent value at...
Design top-K tracker with linked lists
Design a data structure that tracks the top-K most frequent keys in a stream. Support operations increment(key), decrement(key), and topK(k) -> list o...
Determine feasible task ordering
You are given n tasks labeled 0..n−1 and a list of dependency pairs (a, b) meaning task a requires task b to be completed first. Implement functions t...
Design streaming test logger and queries
Implement a streaming logger and two query operations for test runs with globally strictly increasing timestamps. 1) Implement log(test_id, timestamp,...
Solve linked list, top-K, and string reduction
Solve the following algorithmic tasks: 1) Given a singly linked list, return the k-th node from the end (1-indexed). Describe one-pass and two-pass ap...
Design test logging and failure-window queries
Build an in-memory service to log test run results and answer two queries. Assumptions: events arrive with strictly increasing timestamps across all t...
Implement version string comparator with extensions
Implement a function compareVersions(a, b) that compares two software version strings. Each version consists of dot-separated numeric components (e.g....
Compute fruit spoilage time in a grid
Given an m×n grid representing kitchen cells: 0 for empty, 1 for fresh fruit, and 2 for spoiled fruit. Each minute, any fresh fruit adjacent (up, down...
Compute prices, distances, and Top-K for orders
Build functions for a food‑delivery analytics module. Data: - Restaurants: id, (x, y) location, menu mapping item -> price. - Orders: id, restaurantId...
Explain and Implement Strings
Question What is a string in programming languages? Inside a struct string{} in Rust, what fields are stored and how would you design and implement on...
Solve LeetCode array & stream problems
Question LeetCode 346. Moving Average from Data Stream LeetCode 249. Group Shifted Strings LeetCode 163. Missing Ranges Remove duplicates from a chara...
Implement weighted-eviction cache
Question Design and implement a weighted cache supporting get(key) and put(key, value, weight) operations. The cache has a total weight limit; when in...
Solve min window & animal conflicts
Question LeetCode 76. Minimum Window Substring: Given strings s and t, return the smallest substring of s that contains every character of t (includin...
Handle palindrome & decimal addition
Question LeetCode 266. Palindrome Permutation Given two non-negative decimal number strings, implement addition that supports a decimal point. https:/...
Match logs to prior queries
Question You receive a stream of strings, each beginning with either "Q:" (query) or "L:" (log). A query consists of space-separated words and should ...
Design a hierarchical path registry
Implement an in-memory hierarchical path registry. Support: create(path, value) to create a new path with an integer value and get(path) to return its...
Identify members lacking specialty coverage
Oscar wants to ensure that every insurance member has adequate access to in-network healthcare providers within a reasonable travel distance. You are ...
Simulate toppling board game outcome
Implement a function that, given the board size N (3–9 inclusive) and a list of move strings, returns one of: "in progress", "player 1 is the winner",...
Design a Balloon Festival Simulator
Implement a class BalloonFestival with the following API and rules. Goal Track hot air balloons (yours and competitors), evolving wind fields, and bal...