Coding & Algorithms Interview Questions
Practice 3,013 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."
"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."
Simulate a Turn-Based Two-Player Game
Design and implement a simulator for a two-player turn-based board game similar to tic-tac-toe. Requirements: - The game is played on an n x n board. ...
Solve Two Coding Interview Problems
You are asked to solve two independent coding problems. Problem 1: Evaluate Nested Math Expressions Implement a function that evaluates a string expre...
Distinguish Permit Requirement Outcomes
Your platform helps determine whether construction projects require permits in different municipalities. The current system can record conditions unde...
Solve Dependency, Prefix, and Cache Problems
Solve the following three coding problems. Problem 1: Determine Whether All Tasks Can Be Completed You are given numTasks, the number of tasks labeled...
Implement bootstrap mean and variance
Given an array of N numeric values, implement a function that uses bootstrap resampling to estimate the sampling distribution of the mean. The functio...
Remove duplicates in linked list
Question Given a linked list, remove all duplicate values so that each value appears only once. Provide solutions for both sorted and unsorted linked ...
Optimize file reading and expression DFS
Question Given a large password file, build a program to read the required password(s) while minimizing memory usage. How would you optimize the space...
Identify Pirate Themes Using Similarity Score Algorithm
Scenario Engineering wants an automated way to spot custom themes that are probably just pirate themes in disguise. Question Write Python that takes t...
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...
Optimize 0/1 to bounded knapsack DP
Solve the 0/1 knapsack problem: given arrays weight[i], value[i] for i=0..n-1 and capacity W, return the maximum value and reconstruct one optimal set...
Design room progression with leaderboard
Design a data structure to simulate a sequence of rooms where players solve tasks and can move only to the next room once finished. Support the follow...
Implement top-K over a stream
Given a high-volume stream of events (e.g., account IDs from new account openings), design and implement a data structure that supports: ( 1) insertin...
Implement ordering with dependency constraints
You are given n items labeled 0..n−1 and a list of precedence constraints edges[i] = [u, v] meaning u must appear before v. Return a valid ordering of...
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...
Troubleshoot CPU, latency, and DNS issues
A) A Linux server’s CPU usage suddenly spikes. What immediate checks and commands would you run (e.g., top/htop, pidstat, perf, iostat), how would you...
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...
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...
Design rotating warehouse simulator with closures
Given an integer array cap[0..n-1] for warehouses 0..n-1 and a sequence of events, simulate package processing. Events: ( 1) "PACKAGE": process one pa...
Design O(1) random-sampling set
Design a data structure that supports insert(x), remove(x), and get_random() that returns a uniformly random element among the present items, all in e...
Minimize Increments to Equalize Path Costs
You are given a perfect binary tree with n nodes, labeled from 1 to n in level-order. For any non-leaf node i, its left child is 2 i and its right ch...