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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Process Mutable Matrix Sum Queries
You are given a 2D integer matrix and a list of queries. There are two query types: - set r c v: update the value at row r and column c to v - get r1 ...
Implement node messaging and path discovery
You have a network where each node knows only its parent and its children and can send messages to its parent and children. 1) Implement a sendMessage...
Implement a Web Crawler with BFS and DFS
Implement a simple web crawler in Python. You are given: - A starting URL. - A function get_links(url) -> list[str] that returns all outgoing links fr...
Implement three interview-style coding tasks
You are given three separate coding tasks, all focused on algorithm and data-structure design. --- Task 1: Longest Bounded-Difference Subarray You are...
Build a least-recently-used cache
Implement a fixed-capacity key-value cache with least-recently-used eviction. Requirements: - get(key) returns the value for key, or -1 if the key doe...
Place Pieces on a Grid
Given integers n and m, and an ordered list figures where each element is one of "A", "B", "C", "D", or "E", construct an n x m integer matrix grid. T...
Compute sum over consecutive-step subarrays
Given an integer array a of length n, call a subarray a[l..r] good if either: - it is strictly increasing by 1 at every step: a[i+1] - a[i] = 1 for al...
Build a Next-Word Predictor
Implement a simple next-word model over tokenized training sentences. You need to write two functions: 1. train(sentences): receives a list of tokeniz...
Implement a sliding-window rate limiter
Problem Design and implement an in-memory rate limiter using a sliding time window. You are given a stream of requests. Each request has: - key (e.g.,...
Solve Two OA Coding Problems
The online assessment included two coding problems: 1. In-place character run compression - You are given an array of characters. - Compress con...
Compute interval mode, BST range sum, exclusive time
You are given several independent coding tasks. A) Most frequent integer covered by intervals You are given an integer range [-M, M] and a list of inc...
Detect and remove matched words in a char stream
You are processing a stream of characters (arriving one-by-one). You are also given a list of target words. Each time a new character arrives, it is a...
Minimize operations to reduce price difference
You are managing an inventory of products and want to adjust their prices. There are n products. The price of the i-th product is given by an integer ...
Maximize total bandwidth of data channel pairs
You are optimizing how information flows through a network of processing nodes. There are n processing nodes. The bandwidth capability of the i-th nod...
Maximize memory capacity with primary-backup servers
You are helping to optimize the capacity of a cloud system. There are n servers, where n is always even. The memory capacity of the i-th server is giv...
Design a scalable URL shortener
Design a highly scalable URL shortening service, similar to Bitly or TinyURL. The service converts long URLs into short links and redirects short-code...
Calculate Daily Driver Pay
You are given a one-day event log for a delivery driver. Each input record is a JSON event with fields such as order_id, event_type, timestamp, and ba...
Rotate a Matrix In Place
Given an n x n integer matrix, rotate it in place by 90 degrees clockwise. As follow-ups, explain how to modify the approach to rotate the same matrix...
Implement AudioStream Mixer
Implement an AudioStream class that mixes multiple named audio tracks on an integer timeline. Requirements: - The constructor receives a fixed list of...
Solve Grid Path and Graph Sampling
This interview note described two coding problems: 1. Grid path with shortest time and lowest cost You are given an m x n grid containing a start...