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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"Literally just signed a $600k offer. I only had 2 weeks to prep, so I focused entirely on the company-tagged lists here. If you're targeting L5+, don't overthink it."
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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."
Most Frequent Call Stack from Profiler Samples
This question evaluates a candidate's ability to design an efficient hashing and frequency-counting solution over sequences, along with careful handli...
Validate a Shopping Cart
This question evaluates the ability to implement robust input and business-rule validation for shopping-cart items, including data integrity checks, i...
Solve interval merge and string dedup problems
You are given three coding questions from a phone screen. Solve each independently. 1) Merge overlapping intervals Input: A list of intervals interval...
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...
Count segments and optimize 3-server assignment
There are two independent programming tasks. --- Problem 1: Transaction Segments You are given: - An integer n, the length of an array. - An integer k...
Aggregate Loans by Ultimate Parent Company
Aggregate Loans by Ultimate Parent Company Each company has at most one direct parent. For every company loan, follow the parent chain to its ultimate...
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 ...
Implement a simplified grep with extensible flags
Problem Implement a simplified version of grep that searches a text file and returns the lines that match a given query string. You should focus on cl...
Solve word path in grid and trapped water
You are given two independent programming tasks. --- Problem 1: Check if a word exists in a 2D character grid You are given a 2D grid board of charact...
Search Monster Battle Strategies
This question evaluates algorithmic problem-solving around deterministic simulation and state-space exploration, focusing on handling transient state ...
Solve two string problems
You are asked to solve the following two coding problems. 1. Count unique Morse code translations You are given an array of lowercase English w...
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...
Implement TF–IDF with sparse matrices
Implement TF–IDF from Scratch (Python + NumPy/SciPy) You are given a list of documents (plain strings). Implement a TF–IDF vectorizer from scratch — n...
Implement a stack supporting max and popMax
Design a data structure that behaves like a stack but also supports retrieving and removing the current maximum value. Implement a class MaxStack with...
Optimize Matrix-Chain Multiplication
Implement minimum_matrix_chain_cost(dimensions). There are n = len(dimensions) - 1 matrices. Matrix A_i has shape dimensions[i-1] x dimensions[i] for ...
Write SQL for first share and closest collaborator
You are given event data about users viewing design files. Assume the following tables: - files(file_id, creator_id) - creator_id is a VARCHAR user ...
Implement BFS-based maze solver
Maze Printing and BFS Solver You are given a 2D grid representing a maze. Each cell of the grid is one of: - '#' – wall (cannot be passed) - '.' – emp...
Track Customer Revenue and Referral Revenue
Track Customer Revenue and Referral Revenue Problem Implement a top-level function that processes an in-memory customer revenue tracker through a lite...
Build a React team builder with role constraints
This question evaluates frontend React skills including component state management, enforcing role-based constraints and invariants, handling user int...
Implement core puzzle/array/grid routines
You may be asked to solve one or more of the following coding exercises (write clean, testable code; discuss time/space complexity): 1) Jigsaw assembl...