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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"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."

"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Implement Batched Undo/Redo Layer
You are implementing a simplified document layer for a design tool. The layer stores properties as a map<string, string>. Implement a class that suppo...
Match people to questions using tags and priorities
You are building a simplified “Q&A matching” feature. You have: - people: N people, where person i has a set of expertise tags P[i]. - questions: M qu...
Find motion intervals above threshold
You are processing data from a single security camera. You are given: - A threshold value T (a real number). - A vector (array) of time-stamped motion...
Implement a Merkle-tree repo diff
You are given two snapshots of a source-code repository on disk, each represented by a root directory path. Implement a Merkle tree over the directory...
Compute graph distance and impacted services
Part A — Graph shortest distance (BFS) You are given an interface representing a node in an unweighted graph: `java interface Candidate { String id(...
Implement Task Management and Duplicate Detection
You are given two independent coding tasks from a software engineering interview. Task 1: Build an in-memory task management system Implement an in-me...
Compute shortest path in a 2D grid
Given an m x n grid where: - 0 represents an empty cell you can move through - 1 represents a blocked cell you cannot enter - movement is allowed in 4...
Minimize changes for k-periodic palindrome
Question Given a string currentPassword (length N) and an integer k (1 ≤ k < N, N ≤ 2·10^5, lowercase letters, N divisible by k), find the minimum num...
Implement hierarchical folder access check
You are asked to simulate a simple hierarchical file system and implement an access-check function. The file system consists of folders arranged in a ...
Implement deposit, withdraw, and transfer in a class
Problem Implement a class AccountService that supports basic money operations on accounts. Operations - deposit(accountId, amount) - withdraw(accountI...
Find Minimum Rooms Needed
You are given a list of meeting intervals, where each interval is represented as [start, end) and start < end. Two meetings conflict if their time ran...
Determine Whether Courses Can Be Completed
You are given an integer numCourses, representing courses labeled from 0 to numCourses - 1, and a list prerequisites. Each prerequisite is a pair [cou...
Compute exclusive execution time from logs
Problem You are given execution logs from a single-threaded CPU that runs n functions labeled 0..n-1. The CPU can run only one function at a time. A f...
Solve graph path, interval deletion, and robbery
Part A — Optimal path with transport modes: You are given a directed weighted graph of a city. Each edge has a travel time and a transport mode label ...
Group GPUs by node and partition by links
Problem: GPU graph grouping and link-maximizing partition You are given a cluster of GPUs represented as a graph: - Each GPU has a unique gpuId and be...
Design a bank with scheduled payments and merges
Design an in-memory banking service that supports the following operations: ( 1) CreateAccount(accountId), ( 2) Deposit(accountId, amount), ( 3) Trans...
Analyze time complexity for dictionary operations
Analyze the time complexity of the following dictionary/hash map operations. (a) Searching for a key: state average-case and worst-case time, and expl...
Compute task order and layered execution
You have N tasks labeled 0..N-1 and prerequisite pairs (a, b) meaning task a must complete before task b can start. Return any valid execution order o...
Debug and Explain Fixes
Given a small codebase with failing unit tests, identify the root causes of the failures, fix the bugs, and explain the defects you found. Add minimal...
Implement minimal RLE encode/decode with max run K
You are given a run-length encoding (RLE) format that compresses a string by grouping consecutive repetitions of a short substring. Encoding format An...