Coding & Algorithms Interview Questions
Practice 2,970 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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"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."
"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."
Design a text editor with undo/redo
Implement a text document editor that supports the following operations: insert(chars) appends characters to the end; delete(k) removes up to k charac...
Compute height of tree with deleted nodes; minimize deletions
You are given a rooted tree (not necessarily binary). Each node has a list of children. Some nodes are marked as deleted = true. Define the effective ...
Implement crawler, dedup, and persistent LRU
Question LeetCode 1236. Web Crawler: Crawl web pages starting from a given URL within the same hostname. LeetCode 609. Find Duplicate File in System: ...
Solve Four Online Assessment Problems
Complete the following four independent coding tasks. For each task, write a function that returns the requested result. 1. Find the best value index ...
Answer common graph, grid, and array tasks
Problem 1: Largest continuous island after filling sea (1D) Humans can convert ocean cells into land by filling them. Input - islands: a 1D array of l...
Implement Price-Time Order Matching
Implement a simplified limit-order matching engine for a stock exchange. You receive a stream of orders. Each order has: - order_id: unique identifier...
Solve Two Array Optimization Problems
This online assessment included two coding problems. Problem 1: Maximize protected city population You are given: - an integer n - an array population...
Build a validated add-sub calculator
Given a string expression, write a function that validates and evaluates it. The expression represents arithmetic using only non-negative integers and...
Solve Array Distance and Wiki Navigation
You are given two independent coding tasks. For each task, clarify edge cases, implement the function, and write meaningful test cases. Task 1: Minimu...
Compute CDF from a PDF Function
You are given a callable function pdf(t) that returns the probability density of a normal distribution at value t. Implement a function cdf(x) that re...
Implement Checksums and Feature Rollout Evaluation
Complete the following two coding tasks in a 90-minute online assessment. An AI coding assistant may be available, but the submitted code must pass th...
Return the longest contiguous subarray with all distinct values
Given an array shows of integers, return the longest contiguous subarray in which all values are distinct (no repeats within the subarray). Function s...
Merge K timestamped lists with timestamp coalescing
You are given k sorted lists (or linked lists) of records. Each record has: - timestamp (integer) - values (an array of integers sorted in non-decreas...
Convert IPv4 Ranges to CIDR Blocks
Implement a function that summarizes a consecutive IPv4 address range using the smallest possible list of CIDR blocks. You are given: - start_ip: a va...
Solve coding and AI-assisted tasks
This interview included several algorithm problems across a phone screen, onsite coding, and an AI-assisted coding round. Solve the following tasks: 1...
Implement Ultimate Tic-Tac-Toe
Design and implement a playable Tic-Tac-Toe system in two parts. Part 1: Standard Tic-Tac-Toe Implement a TicTacToe class for a standard 3x3 board. Re...
Find Shortest Covering Substring
Given two strings source and target, find the shortest contiguous substring of source that contains every character from target, including duplicate o...
Implement CSAT tracking and call timing
You were asked to solve two coding problems. Problem 1: Implement a rolling CSAT tracker Implement a class CSATTracker for customer-satisfaction score...
Implement a Capacity-Bounded Cache
Implement an in-memory key-value cache with a fixed capacity. The cache must support the following operations in constant time on average: - get(key):...
Find an Exit in a URL Maze
You are given a starting URL for a web-based maze. Each URL represents one room in the maze. Your task is to write a program that discovers whether th...