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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Implement sparse matrix addition and multiplication
Implement sparse-matrix operations with explicit error handling. Sparse matrix A matrix A has dimensions r x c and is sparse, meaning most entries are...
Solve Quickselect, Tree Distance, and Prefix Substrings
You are given three independent coding tasks. 1. Implement Quickselect - Given an unsorted integer array nums and an integer k, return the k-th sma...
Select transactions to maximize fees under size
Problem: Max-fee block assembly You are given N transactions. Each transaction has: - id (unique) - size (positive integer) - fee (non-negative intege...
Validate an IPv4 address string
Given a string s, determine whether it is a valid IPv4 address. A valid IPv4 address: - Has exactly 4 parts separated by dots (.): x1.x2.x3.x4 - Each ...
Design a satellite propagation simulator
Question Implement a SatelliteNetwork class that simulates message propagation over an undirected satellite graph. The class consumes a stream of inst...
Predict most likely next word from training data
You are given tokenized training data consisting of multiple sentences (each sentence is a list of words). Build a lightweight model/data structure th...
Flatten a nested JSON object
Problem You are given a JSON-like value representing an object that may contain: - Objects / dictionaries (string keys) - Arrays / lists - Primitive v...
Maximize Value Under a Budget
You are given an array of items. Each item has a price and a value, and you are given a total budget. Each item can be purchased at most once. Impleme...
Build a Least-Recently-Used Store
Implement an in-memory key-value store with least-recently-used eviction. The store is initialized with a positive integer capacity and supports two o...
Compute Balances and Minimize Settlements
You are building a daily ledger service. A transaction record has three fields: timestamp, user_id, and delta_amount. delta_amount can be positive or ...
Merge overlapping time intervals
Problem: Merge Intervals You are given an array of intervals intervals, where each interval is a pair [start, end] with start <= end. Merge all overla...
Implement Chat Event Counter
Design an in-memory counter for chat activity. You need to implement a class with the following two methods: `text processEvent(userId: string, chatId...
Implement greedy decoding and beam search
You are given access to an auto-regressive language model that can score the next token based on a prefix. Assume: - next_logprobs(prefix_tokens) -> M...
Generate Available 30-Minute Time Slots
You are implementing availability generation for a scheduling service. Given: - start_datetime: the inclusive beginning of a requested date-time range...
Implement comment sorting and nesting
You are given mock comment data on the frontend. Each comment has: - id: unique comment ID - userId: author ID - timestamp: creation time - content: c...
Return the longest contiguous subarray with all distinct values
Given an array shows of integers, return the longest contiguous subarray in which all values are distinct (no repeats within the subarray). Function s...
Merge overlapping weekly time intervals
You are given a list of time intervals representing meetings. Each interval is a pair of strings in the format: - "<Day> <H>:<MM>" (24-hour time) - <D...
Implement spreadsheet undo/redo operations
Problem Design a data structure that simulates Undo/Redo for a simplified spreadsheet editor. A user performs a sequence of operations on cells. Each ...
Implement Game Physics and Block Mining
You are given two independent coding tasks from the same interview category. Solve both. Task A: Flappy-Bird-Style Jump Boundary Function Implement a ...
Implement CSAT tracking and call timing
You were asked to solve two coding problems. Problem 1: Implement a rolling CSAT tracker Implement a class CSATTracker for customer-satisfaction score...