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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Design an In-Memory Database
Implement a simple in-memory database with a flexible, schema-less record model. Requirements: - Each record is a mapping from column_name to value. -...
Can one car serve all riders?
This question evaluates understanding of interval scheduling and conflict detection, testing skills in time-interval reasoning, sorting, and efficient...
Implement a Streaming VMStat Alert
This question evaluates streaming data processing skills, sliding-window counting algorithms, and efficient online state management for metric monitor...
Implement a Versioned Key-Value Store
Design and implement an in-memory versioned key-value store. Requirements: - put(key, value, timestamp): store value for key at the given integer time...
Compute Inherited Role Privileges
You are given n roles. The array initialPrivileges has length n, where initialPrivileges[i] is the list of privileges directly assigned to role i. You...
Build Ranked Feed With Photo Batching
You are given a list of feed objects. Each object has: - id: a unique string - type: one of Normal, Video, or Photo - score: a numeric ranking score C...
Solve delimiter and CSV tasks
This question evaluates skills in string parsing and bracket balancing, CSV/file parsing and joining, computation of derived values, and sorting, emph...
Probability That One Fair Die Beats Another
Probability That One Fair Die Beats Another Two fair dice, A and B, are represented by integer arrays. Each array element is one physical face, so dup...
Rotate a Matrix In Place
This question evaluates proficiency in in-place matrix and array manipulation, understanding of spatial transformations, and consideration of space an...
Find High-Intensity Time Periods
Given a list of time-series readings, where each reading is {timestamp, intensity}, and a numeric threshold, return all maximal time periods during wh...
Solve Balanced Permutations and Tree Reversals
You have 90 minutes to solve the following two independent coding problems. Problem 1: Balanced Prefix Values in a Permutation You are given a permuta...
Implement Game Metadata Lookups
You are given a list of game metadata records. Build an in-memory representation that can store each game's name, release date, platforms, genre, publ...
Design Hierarchical Permission Checks
You are given a hierarchy of groups represented as a tree, for example World -> Country -> City. Each advertiser can be granted access at any group no...
Solve Grid Path and Graph Sampling
This question evaluates graph algorithms and probabilistic/combinatorial reasoning, covering multi-criteria shortest-path optimization (minimizing tra...
Implement a Parallel Image Processor
This question evaluates understanding of parallel and process-based concurrency, batch image-processing pipelines, transform correctness, and per-job ...
Implement a Versioned Key-Value File Store
Implement an in-memory file store that supports progressive requirements. Operations include set(key, value), get(key), delete(key), scan(), scan_pref...
Simulate Plant Infection With Controlled Burning
You are given an R by C grid of plants. Each plant is initially healthy, infected, recovered, or dead. A plant has up to four orthogonal neighbors. De...
Find First Anagram Occurrence
Given two strings text and pattern, return the starting index of the first substring in text that is an anagram of pattern. If no such substring exist...
Solve substring and worker assignment
The interview included two algorithm problems: 1. Shortest covering substring: Given two strings s and t, return the shortest contiguous substring of ...
Validate bracket sequence
Given a string s containing only the characters (, ), [, ], {, and }, determine whether the brackets are properly matched. A string is valid if: - Eve...