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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Count Same-Day Registered Posters
You are given two tables: `text users - user_id: unique identifier for a user - registered_at: timestamp when the user registered posts - post_id: uni...
Simulate Threshold Grid Infection
This question evaluates understanding of discrete grid-based simulations and local state-transition rules, focusing on modeling infection spread, neig...
Compute Available Offers per User
This question evaluates event-stream processing, stateful per-user counting, and time-window filtering competencies, requiring correctness with ordere...
Implement a Snapshot Set Iterator
Implement a data structure SnapshotSet<T> with the following interface: `java interface SnapshotSet<T> { void add(T e); void remove(T e); ...
Implement Order Modification Feature
You are given an existing C++ trading system with a client/server architecture. The current system already supports two request types: - AddOrder(orde...
Compute account balances with rejection and overdraft
You are given a list of transaction records as strings. Each record has the format: ` account_id,timestamp,currency,amount ` - account_id: string iden...
Compute maximum score using up to 3 categories
Problem A library runs a summer reading program. Each book a student reads earns a certain number of points, and each book belongs to a category. A st...
Implement Food Delivery Billing
This question evaluates proficiency in implementing business billing rules, time and distance-based fee calculations, timestamp arithmetic, numerical ...
Implement map serialization and deserialization
You are given an in-memory map (dictionary) from strings to strings. Implement two functions: - string serialize(map<string, string> m) - map<string, ...
Implement Sliding-Window Rate Limiter
This question evaluates understanding of time-based sliding-window rate limiting, per-user quota enforcement, efficient in-memory data structures for ...
Minimize travel cost with two cities
You are scheduling candidates to attend an onsite interview. Each candidate i can fly to New York for cost c1[i] or to San Francisco for cost c2[i]. C...
Design a nested-list iterator
You are given a nested structure that can contain integers or further lists. Design an iterator over this structure that returns integers in left-to-r...
Solve word count, node, segmentation, stock tasks
You have four tasks: 1) Count words with explicit rules: Given a text document, return the number of words. First define precisely what qualifies as a...
Match alphanumeric patterns in a stream
Given a reference 7–8 character alphanumeric code and four candidate codes, select the exact match as quickly as possible. Design a system that: - Eff...
Refactor rock–paper–scissors for config and ties
Refactor an existing Rock–Paper–Scissors tournament with three robot players so that the number of rounds is configurable and the system also tracks t...
Implement an expiring GPU-credit manager
Implement an expiring GPU-credit manager for a cloud provider. Each user receives credit grants with an amount and an expiration timestamp. Support: (...
Generate unique permutations with duplicates
Given an array of integers that may contain duplicates, generate all unique permutations. Ensure no duplicate permutations are returned even if some v...
Implement Connect Four with bottom push-up
Implement a Connect Four variant with bottom push-up. In standard Connect Four a dropped disc falls to the lowest empty cell of a column. In this vari...
Compute pipeline order from dependencies
You are given a set of pipelines and a list of directed dependency pairs (A, B) meaning pipeline A depends on pipeline B and therefore B must run befo...
Compute shared free time intervals
You are given schedules for multiple employees. schedules[i] is a list of busy intervals for employee i, where each interval is half-open [start, end)...