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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"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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Solve Four Coding Assessment Tasks
Complete the following four independent coding tasks. 1. Find the day a cumulative visit target is reached You are given an array visits, where visits...
Implement calculator and graph connectivity
Answer the following coding problems: 1. Implement an arithmetic expression evaluator. Given a string containing non-negative integers, spaces, +, -, ...
Compute outer boundary of an N-ary tree
You are given the root of a rooted N-ary tree. Each node contains: - An integer value. - An ordered list of children from left to right (0 or more chi...
Compute max profit with forced trades
Given an array prices where prices[i] is the stock price on day i, solve two related tasks under a forced-trade constraint: (a) Exactly one transactio...
Schedule batched register operations optimally
Problem You are given a text file that describes batches of register operations (reads and writes) on integer-indexed registers. Your task is to sched...
Solve jump maximization and palindromic path queries
You are given two independent algorithmic problems. --- Problem 1 — Jump game with special destinations (maximize score) You are given an integer arra...
Build User Journey Path Summary
Implement a function build_summary(logs) -> str that summarizes user journeys as a trie-like path tree. You are given a list of action logs. Each log ...
Implement obstacle-course run statistics
You are given a TypeScript codebase for tracking race results on an obstacle course. - A Course has a fixed number of obstacles. - A Run stores the ti...
Implement one-cluster k-means
Given n points in d-dimensional space, implement k-means clustering with squared Euclidean distance for the special case k = 1. Return the single cent...
Solve Two String Problems
The interview included two coding questions: 1. Exactly one edit apart Given two strings s and t, determine whether they are exactly one edit apart...
Solve four classic algorithm problems
You are given four independent coding tasks. For each task, implement the required function. --- Problem 1: Zigzag level-order traversal of a binary t...
Compute nearest dashmart distances for queries
You are given an m x n grid where each cell is one of: -1 for a wall (impassable), 0 for a dashmart (a store), and INF = 2^31 - 1 for an empty room. M...
Implement crawler and bracket validator
Implement two tasks: ( 1) Write a function crawl(start_urls, fetch, max_depth, domain_filter) that visits pages starting from the given seed URLs usin...
Detect cycle in a directed graph
Given a directed graph represented by an adjacency list with n vertices and m edges, determine whether the graph contains a cycle. Describe and implem...
Heapify an array into a max-heap
Given the array [6, 15, 2, 4, 3, 8, 19], apply heapify to build a max-heap using the standard in-place bottom-up method with a 0-indexed array represe...
Implement Binary Search in C++
From scratch in C++, implement binary search over a sorted array to locate a target value. Provide a correct iterative implementation, handle not-foun...
Implement Python LRU cache with varargs
Implement an LRU cache in Python as a decorator cache(maxsize) that memoizes a target function's results. Must support positional args, args, and *kwa...
Implement string-based big integer multiplication
Question Implement multiplyStrings(a, b) to multiply two non-negative integers given as decimal strings and return their product as a decimal string. ...
Find longest unique-character substring
Given a string s, return the length of the longest substring without repeating characters. Explain and implement an O(n) sliding-window solution using...
Find root from child adjacency lists
You're given an unordered list describing a rooted n-ary tree. Each item is a record of the form {id: int, children: set<int>} listing a node's direct...