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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Generate Per-Position Guess Feedback
You are building a word-guessing feedback function. Given two strings, target and guess, of the same length, return an integer array feedback where ea...
Maximize watched duration under consecutive-sum limit
You have a list of videos in a feed. Video i has duration d[i] (positive integer). A user has an “attention span” limit A. You want to select a subset...
Implement 2D convolution forward pass
Problem Implement the forward pass of a 2D convolution (conv2d) from scratch (no deep learning libraries). You are given: - Input tensor x with shape ...
Implement Stable Softmax
Implement a function that computes the normalized exponential values of a list of real numbers. Given an array x of length n, return an array p of len...
Implement Concurrent Any-True Shot
You are given a function shot(index) -> bool. Each call may take between 1 and 10 seconds to return. Implement volleyShot(indices) -> bool for a list ...
Implement a BFS web crawler
A web crawler starts from a URL and explores reachable pages level by level. You are given: - start_url: string - An interface fetch_links(url: string...
Compute days until a higher reading
You are given an array readings[] representing sensor values over consecutive days (e.g., temperatures). For each day i, compute how many days you mus...
Transform sparse time-code stream to dense rows
Problem You are given: - A fixed set of M distinct codes (strings). The column order of the output matrix is the lexicographic order of these codes. -...
Implement common data-structure and JS tasks
You are given several independent coding tasks that appeared across an OA and frontend-focused interviews. Implement each as specified. 1) Time-based ...
Implement a versioned hash map with snapshot
VersionedHashMap (time-travel key-value store) Design and implement a data structure VersionedHashMap<K, V> backed by a hash map that supports retriev...
Solve a Key-Door Corridor Maze
AI-assisted coding round. You may use an AI coding assistant, but you are responsible for debugging the implementation and validating the test cases. ...
Find duplicates in a list efficiently
Given a Python list that can contain integers (possibly negative) and may be very large, write code and explain approaches to find all values that app...
Process exchange prints, volume checks, and client orders
You are writing a broker program that interfaces with an exchange via a stream of commands on stdin. You must process commands in order and write requ...
Find Unique Target-Sum Pairs
Given an integer array nums and an integer target, return all unique pairs of values whose sum equals target. Requirements: - Each returned pair shoul...
Implement Interval Overrides and Top-K Strings
Solve both coding problems below. Problem A: Apply Override Intervals You are given a set of time intervals representing normal usage periods. Each us...
Solve Two Array Optimization Problems
You are given two coding problems from the same interview round. Problem 1: Split a gold chain fairly An array weights represents the weights of conse...
Design an Elevator System and Scheduler
Design an object-oriented elevator system. Define core classes and interfaces (elevator, controller, request, floor, buttons, sensors) and their inter...
Approximate Pi from Random Points
You are given an array pts of points sampled uniformly at random from the unit square [0, 1] x [0, 1]. Each point is represented as an array [x, y], w...
Design in-memory payment and friendship system
Design and implement an in-memory payment system with simple social features. The system processes a sequence of requests that can: 1. Register a user...
Implement account scheduler with locking and LRU
Design a class AccountScheduler that manages the time-based availability of a fixed set of account IDs. Initialization You are given: - accounts: a li...