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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"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."
Compute Jaccard similarity between two strings
Jaccard Similarity of Two Strings Given two strings a and b, compute their Jaccard similarity based on token sets. Tokenization rules - Convert to low...
Retain Top K Elements
Given a list of integers nums and an integer k, return a new list formed from the original list after removing every element except the k largest elem...
Build a simplified Wordle game in React
Problem: Implement a simplified Wordle in React Build a small Wordle-like game UI using React. Requirements - The game chooses a single answer word by...
Reverse Words While Preserving Spaces
Implement a C++ function that reverses the order of words in a string. Assume a word is any maximal sequence of non-space characters, and the input co...
Implement flood fill using BFS and DFS
Problem You are given a 2D grid image of size m × n, where each cell contains an integer color value. You are also given a starting cell (sr, sc) and ...
Solve four OA algorithm problems
You are given four independent coding questions. 1) Count square subgrids (multiple queries) For each query, you are given two integers R and C repres...
Filter ads by a single rule
Single-Rule Ad Filter Context When a user watches content, the system needs to filter an ad pool to find ads that match one rule. Implement a lightwei...
Solve two grid problems (islands + min-cost path)
You are given two separate coding questions. Problem A: Count distinct islands (translation-equivalent) Given an m x n binary grid grid (0 = water, 1 ...
Print all odd numbers from an integer list
Problem Given a list/array of integers nums, print (or return) every odd number in the list, in the same order they appear. Clarifications / follow-up...
Solve Maze and Suffix Problems
Solve the following two coding problems. Problem A: Find the shortest path through a maze with keys and doors You are given a 2D grid representing a m...
Debug and refactor a legacy module
Given a legacy module named DasherPicker and a failing test suite, systematically debug and refactor the code while following a provided review checkl...
Minimize calls to find all bad test pairs
You have \(n\) atomic tests \(t_1, t_2, \dots, t_n\). You are given access to a black-box function: `python bool runTest(set<Test> S) ` which behaves ...
Assign tasks to workers with types and accounts
You are implementing a task scheduler. There are W workers (IDs 0..W-1) and N tasks (IDs 0..N-1). Each task i arrives at time arrival[i] (non-decreasi...
Solve Sliding Window and Grid Search
In a Software Engineer phone screen, the candidate was asked to solve two coding problems. 1. Longest substring with at most k distinct characters ...
Find Shortest Square-Sum Path
Given a positive integer n, find one shortest path from 0 to n where each step adds a perfect square number. Equivalently, return a shortest sequence ...
Implement cache and gift assignment system
You are given two independent programming problems. --- Problem 1: Implement a bounded key–value cache Design a data structure that stores key–value p...
Implement an in-memory file system
Implement an in-memory file system supporting basic directory and file operations. You must support the following methods (names are illustrative; any...
Implement a Fixed-Capacity Deque
Design and implement a fixed-capacity double-ended queue. The data structure is initialized with an integer capacity k and must support the following ...
Write SQL Data Transformation Queries
Use SQL to solve the following data transformation tasks. Assume standard SQL features are available, including window functions and recursive common ...
Implement Several Core Algorithmic Components
Solve the following independent coding tasks. 1. Implement an LRU cache. Design a class LRUCache with: - LRUCache(int capacity): initializes the...