Coding & Algorithms Interview Questions
Practice 3,469 real Coding & Algorithms interview questions for 2026. Covers companies like Meta, Amazon, Google, Uber, and Microsoft. Real questions from actual interviews with detailed solutions — ideal for focused interview preparation. Coding & Algorithms interview questions are the single most common technical gate for software engineering roles and are used to evaluate problem framing, algorithm selection, complexity trade-offs, correctness, edge-case reasoning, and clear communication under time pressure. Expect this category to appear in early technical screens and repeatedly across onsite loops at companies that weight it heavily (notably Meta, Google, and Amazon). Interviews will test arrays and strings, trees and graphs, dynamic programming, hashing and two‑pointer techniques, and the candidate’s ability to test and optimize code in a shared editor. Prepare with timed mock interviews, practice in the same editor you’ll use live, and build a progressive schedule that moves from fundamentals to medium/hard problems; typical candidates invest several weeks to a few months of focused practice depending on seniority and target company.
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Solve Three Algorithmic Tasks
You were asked three coding problems: 1. Count events inside a time window - You are given an initial collection of event timestamps in HH:MM:SS fo...
Wrap Matching Substrings in Bold Tags
During a machine learning engineer phone screen, the coding task was: You are given a string text and a list of strings patterns. Return a new string ...
Implement Calendar Layout and String Packing
The interview reportedly included two separate coding exercises: 1. Day-view calendar layout - You are given a list of events for a single day. Eac...
Merge Weekly Time Intervals
You are given a list of time intervals within a single week. Each time is written as a day-of-week plus a 24-hour clock, for example Sat 13:00 or Mon ...
Match Bookings to Payments
You are given two unsorted lists: - bookings: each record contains at least a unique booking_id - payments: each record contains at least a booking_id...
Count Islands in a Grid
This question evaluates skills in graph traversal and grid connectivity detection, testing competency in reasoning about adjacency, state management, ...
Solve array, tree, and maze problems
This question evaluates algorithmic problem-solving across arrays, binary trees, and grid pathfinding, testing competencies in array traversal and vis...
Maximize Earnings by Converting Days Off into Workdays
Maximize Earnings by Converting Days Off into Workdays An employee is planning a work schedule for n consecutive days. For day i you are given whether...
Design an Editable Text Buffer
This question evaluates data structure design, mutable state management, undo/redo semantics, and prefix-based autocomplete indexing with dynamic freq...
Check connectivity between two subway stations
You are given a description of subway stations A, B, C, D, E, ... as a graph. For each station, you are told which other stations it directly connects...
Compute square root with precision
Given a non-negative integer val and a non-negative integer precise, compute the square root of val without using any built-in square-root function. R...
Debug Queues and Solve Arrays
This multi-part question evaluates competencies in data structures (heap invariants and in-place array manipulation), concurrent programming (designin...
Implement weighted random choice
This question evaluates understanding of weighted random sampling, probability distributions, input validation, and algorithmic time and space complex...
Compute subtree sums with tree DFS
You are given an undirected tree with n nodes labeled 1..n and n-1 edges. The tree is rooted at node 1. Each node i has an integer value val[i]. Retur...
Reverse even numbers in a list
Given an integer array nums, remove all odd numbers and return the remaining even numbers in reverse order (preserving no other ordering constraints)....
Implement an in-memory database with record locking
Implement an in-memory key–record database that supports basic CRUD on fields plus an exclusive lock per record. You are given a sequence of queries. ...
Implement Cache and Count Components
You are asked to solve two independent coding problems in this session, each followed by a short discussion. This mirrors a 60-minute Amazon SDE codin...
Find top co-viewed products
You are given a list of user browsing sessions, where each session is a list of product IDs, a target_product, and an integer k. A product should be c...
Minimum Round-Trip Flight Cost
You are planning a round trip and want to spend as little as possible on flights. You are given two integer arrays of equal length n: - departure[i] —...
Maximum Length of a Word Selection With All Unique Characters
You are given an array of lowercase strings words. Select a subset of these words (zero or more, chosen in any order) and concatenate them. The select...