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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Place items into earliest fitting bins
You are given k items with sizes items[0..k-1] and n bins with initial capacities caps[0..n-1]. Process items in order; for each size x, place it into...
Implement power, reduce string, parse tree, debug maze
1) Implement fast exponentiation (pow) Implement a function pow(x, n) that returns \(x^n\). - Inputs: a floating-point base x and an integer exponent ...
Implement multiple coding round problems
Solve the following coding problems. 1) Bus schedule (next departure) Given: - A sorted list buses[] of bus departure times (minutes since 00:00). - A...
Implement distinct islands and sliding maxima
1) Given a binary grid where 1 represents land and 0 represents water, count how many distinct island shapes exist. Two islands are considered the sam...
Implement a Tic-Tac-Toe game class
Problem Implement a class that supports playing an n × n Tic-Tac-Toe game. Requirements Create a class TicTacToe(n) with: - move(row, col, player) -> ...
Validate a bracket string
Given a string s containing only the characters '(', ')', '{', '}', '[', and ']', determine whether the input string is valid. A string is valid if: 1...
Detect k events in a sliding window
Implement an algorithm that, for each user, determines whether there exists a set of at least k ACH credit events from distinct device_ids within any ...
Implement multiplication without using the multiplication operator
Implement int multiply(int a, int b) without using * or /. You may use +, −, bitwise operators, and shifts. Requirements: - Handle negatives, zero, an...
Implement sliding-window rate limiter with dual thresholds
Implement getRequestStatus(urls: List[str]) -> List[str]. The i-th entry in urls represents a single incoming request at timestamp t = i seconds (t st...
Optimize bread-factory pipeline for max profit
You can assemble a production line by choosing modules of three types: Mixers, Ovens, Packers. Each module i has (type, build_cost_i, throughput_i uni...
Implement streaming k-way merge with constraints
Implement a function merge_k(iterators, N) that returns the first N items of the global ascending order from k sorted, potentially unbounded iterators...
Review checkout code for defects and privacy
You are reviewing a supermarket checkout implementation. Identify and prioritize issues and fixes across: (a) monetary correctness (avoid floating poi...
Fix failing tests and refactor code
You're given a small Python repo. After creating and activating a clean virtual environment, installing requirements, and running "pytest -q", two tes...
Compute average unique pins per user
Task: Average Unique Pins Per User You are given a mapping from user IDs to their lists of pin IDs. Implement a function that computes the mean number...
Merge words by head-tail chaining
Given a list of lowercase words, merge them into a single string by repeatedly chaining words where the last character of the current string equals th...
Implement a Rollback Key-Value Store
Design and implement an in-memory key-value store that supports rollback. The store should support at least the following operations: - set(key, value...
Explain Java volatile semantics
What does the volatile keyword guarantee in Java's memory model? Describe visibility, ordering (happens-before), and restrictions on instruction reord...
Describe std::string copy semantics
In C++, what happens with std::string when you write: std::string a = "123"; std::string b = a; Describe which operations are invoked (copy constructi...
Sort products by price and attention score
You are given a list of strings, each formatted as "product,price,attention". Parse the list into records and return the product names sorted to prior...
Find smallest start index avoiding left exit
You are given an integer array jump of length n (0-indexed). If you are currently at index i, your next position becomes i + jump[i] (a positive value...