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."

"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
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...