Coding & Algorithms Interview Questions
Practice 2,960 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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Assign meetings to rooms with delays
You are given: - An integer n (number of meeting rooms, labeled 0..n-1). - A list of m meetings meetings[i] = [start_i, end_i) with start_i < end_i. A...
Compute top-N items from log stream
Problem You are given application logs containing events with an itemId. Each log line may contain extra fields, but you can extract the itemId from e...
Maximize capacity with primary-backup pairing
You are given n servers, where server i has memory capacity memory[i]. A valid system must contain an even number of servers. If the system contains 2...
Find shared courses between student pairs
Problem Set (Coding) You are given multiple coding questions from an interview. Implement each function as described. --- 1) Course Overlap You are gi...
Implement sparse matrix storage, addition, and multiplication
Design a way to store a sparse matrix (most entries are zero) and implement efficient operations. You are given matrices using their non-zero entries:...
Compute minutes since last train departure
You are given a daily train timetable as a list of departure times (24-hour format HH:MM). Given the current time (also HH:MM), find the most recent d...
Compute Latencies and Search Grid Path
You are given two coding tasks from an internship interview. Task 1: Compute Message Latency from CSV Logs Two systems, ComputeA and ComputeB, exchang...
Convert stack samples to trace events
Question Implement convertToTrace(samples) that, given a chronologically ordered vector of stack samples (each sample contains a timestamp and a call-...
Implement and Optimize Vector Multiplication
Implement vector–vector multiplication for dense vectors (e.g., dot product). Then, describe how you would optimize the implementation for a parallel ...
Compute currency conversions with graph algorithms
Question You are given a set of pairwise currency exchange relations such as A:B = 1:1.5 and B:C = 1:1.5, meaning 1 A = 1.5 B and 1 B = 1.5 C. Design ...
Design an in-memory database with TTL and history
Design and implement an in-memory key–field–value store with monotonic timestamps. Keys and fields are strings; values are integers. Provide these API...
Group words into anagram lists
Given an array of strings, group the words into lists of anagrams and return the collection of groups in any order. For example, ["abc", "cab", "edf"]...
Test easy–medium array/string tasks
For typical easy–medium array and string problems, list the most important edge cases you would test (e.g., empty input, single element, duplicates, a...
Search target in unknown-length sorted array
You have read-only access to a sorted, increasing array-like interface of unknown length that supports get(i), which returns a valid integer for in-bo...
Debug using logs and allocate tasks
You inherit a service where unit tests pass locally, but production logs show intermittent errors. Without a debugger, outline a step-by-step debuggin...
Compute nested depth-weighted sum
You are given a nested structure containing integers and lists (e.g., [1, [4, [6]]]). Define depth of the top-level as 1. Compute the total sum of all...
Implement DFS for connected components
Given an undirected graph with n nodes (1 ≤ n ≤ 200, 000) and an edge list, implement depth-first search to compute (a) the number of connected compon...
Choose root to minimize edge reversals
Problem You are given a connected graph with n nodes labeled 0..n-1 and n-1 directed edges. If you ignore directions, the edges form a tree (i.e., the...
Implement sequential and parallel URL requests
You are given a list of URL strings. For each URL, send an HTTP GET request and return the responses. Output format Return a list of objects: - url: t...
Merge intervals and design rating APIs
Problem 1: Merge overlapping intervals You are given a list of closed intervals intervals, where intervals[i] = [start_i, end_i] and start_i <= end_i....