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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Infection Spread on a Grid (Cellular Automaton)
Infection Spread on a Grid (Cellular Automaton) You are simulating how an infection spreads across a 2D grid of cells over a sequence of discrete time...
Compute Minimum Task Completion Time
You are given n tasks numbered from 0 to n - 1. Each task i takes durations[i] units of time to execute. You are also given a list of directed depende...
Determine if all courses can be completed
You are building a planner for a training program with n courses labeled 0 through n - 1. You are given a list of prerequisite pairs prerequisites, wh...
Implement an Alternating Tic-Tac-Toe Game
Implement a Tic-Tac-Toe game for two players. Requirements: 1. The board is a standard 3 x 3 grid. 2. Players do not need to be passed into each move....
Replace Delimited Tokens in a String
Given an input string s and a dictionary replacements mapping keys to replacement strings, replace every placeholder in s with its corresponding value...
Expand Nested Repetition Expressions
Implement a function that expands a valid encoded string containing nested parenthesized repetition expressions. Rules: - Ordinary characters are appe...
Shortest Path in a Grid with Blocked Cells
Shortest Path in a Grid with Blocked Cells You are given an m x n grid that represents a floor plan. Each cell is one of: - 0 — an open cell you can w...
Implement Byte Formatting and Cafeteria Billing
You need to solve two independent programming tasks. Task 1: Format a byte count Given an integer bytes representing a size in bytes, return a formatt...
Calculate Bowling Game Score
Implement a function that calculates the total score of a complete ten-pin bowling game. Input: a list of integers rolls, where each integer is the nu...
Simulate rover movement on a grid
You are building a rover navigation simulator. The exercise is incremental: you implement a single rover on a 2D grid, then extend the design to many ...
Solve Matrix and Array Distance Problems
You are asked to solve two coding problems. Problem 1: Shortest Path in a Binary Matrix Given an m x n matrix containing only 0 and 1: - 0 represents ...
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...
Debug and extend obstacle-run statistics classes
Problem: Obstacle course run statistics (debug + implement) You are building software to track how long racers take to complete an obstacle course. Do...
Spreading Contagion on a Grid
Spreading Contagion on a Grid You are given an m x n integer grid cells. Each entry has one of three values: - 0 — an empty location (no unit present)...
Find Earliest Column With One
You are given access to a binary matrix through an API rather than direct storage. The matrix has m rows and n columns. Each row is sorted in nondecre...
Solve Bracket Matching and Tree Width
Solve both coding problems below. Problem 1: Validate Balanced Brackets Given a string s containing only the characters (, ), {, }, [ and ], determine...
Simulate an exchange and participation-rate trading
Implement a simplified trading simulation in three parts. Part 1 — Process market data / exchange interaction (order book) Design a minimal limit-orde...
Implement an Expiring Record Store
Implement a level-based in-memory record store. The store contains records identified by a string key. Each record contains fields, where each field i...
Implement Multi-Head Attention from Scratch in NumPy
Implement multi-head scaled dot-product attention from scratch using only NumPy. This is the core building block of a Transformer block, and you must ...
Find the Most Common Visit Pattern
You are given a list of web visit logs. Each log record contains userId, timestamp, and page. For each user, sort that user's visits by timestamp. A l...