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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"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."
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Design a Randomized Multiset
Implement a data structure for integers that allows duplicate values and supports the following operations in expected O(1) time: - insert(val): Add o...
Solve Knight and Reversal Problems
The online assessment contained two coding problems: 1. Generalized knight shortest path: Given an integer n, consider an n x n chessboard with coordi...
Merge Sorted Arrays In Place
You are given two non-decreasing integer arrays. - A has length m + n. - The first m elements of A are valid sorted numbers. - The last n elements of ...
Implement Recipe Storage CRUD
Implement an in-memory RecipeStore that supports CRUD operations for recipes. Each recipe contains: - id: a string identifier in the form recipe<n> - ...
Implement URL Shortening Codec
Implement a small in-memory URL-shortening component in a pair-programming interview. Expose two methods: shorten(long_url: str) -> str, which returns...
Build a Fuzzy Keyword Index
This question evaluates string-processing, text-indexing, approximate string-matching, and data-structure design skills for supporting many repeated q...
Find Top K Largest Numbers
This question evaluates proficiency with heap/priority-queue data structures, selection algorithms, and the ability to analyze time and space complexi...
Minimize deaths in spreading plant infection
This question evaluates a candidate's ability to model and simulate dynamic grid processes, reason about infection propagation and delayed state chang...
Count User Journey Prefixes
This question evaluates the ability to reconstruct per-user action sequences from timestamped logs, aggregate and count path prefixes, and apply data-...
Write an average-income function
This question evaluates proficiency in data manipulation and basic statistical aggregation, particularly handling missing values and computing average...
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...
Generate All Valid Combinations of Balanced Parentheses
Generate All Valid Combinations of Balanced Parentheses Given an integer n representing the number of pairs of parentheses, generate all distinct stri...
Find and Merge Camera Alert Intervals
You are given surveillance camera readings as time-series data. Each reading is a pair (timestamp, value), sorted by timestamp. A camera is considered...
Fixed-Width Text Display
Fixed-Width Text Display You are building a text display that renders a sequence of words inside a viewport of a fixed character width maxWidth. The d...
Implement array parity and tree level views
This question evaluates proficiency in array frequency analysis and binary tree traversal, testing skills in data structures, correctness reasoning, a...
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 ...
Implement an In-Memory File System
Design an in-memory file system that supports file management, search, user ownership, capacity limits, copying, and compression. Each file has a uniq...
Solve two online assessment problems
This two-part prompt evaluates algorithmic problem-solving skills: the first problem tests optimization under index-based movement and number-theoreti...
Make a Parentheses String Valid
Given a string s containing lowercase English letters and the characters '(' and ')', remove the minimum number of parentheses so that the resulting s...
Find Maximum Envelope Nesting
This question evaluates algorithmic problem-solving skills, particularly reasoning about multi-dimensional ordering, sequence optimization, and time-c...