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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"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."
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Implement Notification Rate Limiter
Implement should_send_notifications(user_id, timestamp) -> bool. You are given two mappings: - each user_id belongs to exactly one team_id - each team...
Sample index from weighted probability distribution
Given an array weights[0..M-1] representing a discrete distribution over M outcomes, implement a function sampleIndex(weights) that returns an index i...
Fetch paginated data from two APIs
Write a function get_enriched_records(api_a_url, api_b_url). api_a_url returns paginated JSON in the form: `json { "data": [ {"id": 1, "ref_id":...
Compute variance of a list in Python
Task Given a Python list of numbers (ints/floats), write code to compute its variance. Requirements - Input: nums: list[float] (length \(n\ge 1\)) - C...
Implement an Alert Execution Engine
You are given an alert client API that provides alert configurations, metric query execution, and notification methods. Implement an alert execution e...
Implement Kubernetes Service Dependency Queries
You are given an in-memory inventory of Kubernetes-like services. Each service has the following fields: `text Service { id: string // ...
Find Path Between Fibonacci Tree Nodes
This question evaluates a candidate's ability to reason about recursive tree structures, map preorder indices to positions in a recursively defined Fi...
Merge overlapping corrections
Implement correctionMerge(corrections). You are given a list of text-correction spans. Each correction applies to an inclusive interval [start, end] a...
Implement Plus One
Given a non-empty array of digits representing a non-negative integer, where the most significant digit comes first and each element is in [0, 9], add...
Maximize block fee with transaction selection
You are given N transactions. Each transaction has: - id (unique identifier) - size (positive integer) - fee (positive integer) You are building a blo...
Design Tic-Tac-Toe With K Players
Design and implement a Tic-Tac-Toe game engine. You are given: - k players, each with a unique player ID or mark. - An n x n board, initially empty. -...
Implement Plurality and Runoff Voting
You are given a list of ballots for an election. Each ballot is an ordered list of distinct candidate names, from highest preference to lowest prefere...
Implement sliding-window timestamped average
Problem Implement a class that maintains a time-based sliding window of records and can return the average score within the current window. Requiremen...
Find cheapest common ancestor in a tree
This question evaluates understanding of tree data structures and ancestor concepts (such as lowest common ancestor) along with algorithmic skills for...
Solve multiple algorithmic interview questions
Below are several independent coding tasks. For each task, implement a function that returns the required output. Assume: - Arrays/lists are 0-indexed...
Group duplicate files by content
Problem You are given a list of files in a filesystem. Each file has: - a full path (string) - a file size in bytes (integer) - file contents (concept...
Design O(1) insert/delete and frequency-weighted random
Problem Design a data structure that supports the following operations in average \(O(1)\) time: 1. add(x) -> bool - Inserts value x into the colle...
Parse logs and count error codes
This question evaluates parsing and sanitizing structured text, extracting specific fields, and performing frequency aggregation of identifiers such a...
Find all quadruplets summing to target
This question evaluates competency in array algorithms, combinatorial search, and handling duplicates with index-uniqueness constraints, and falls und...
Compute dependency load factors in a DAG
This question evaluates understanding of graph theory and algorithms, specifically reachability and dependency analysis in a directed acyclic graph, a...