Interview questions

Design Hit Counter

Design a hit counter that records timestamps of hits and returns the number of hits in the past 5 minutes (300 seconds). The challenge is…

Companies: Adyen, Apple, Cisco, Databricks +5

Array · Binary Search · Data Stream · Design

Last reported Nov 2026

String Reconstruction from Fragments

Given an array of strings representing consecutive fragments of an original string, reconstruct the original string by arranging the fragments in the correct order. Each…

Companies: Microsoft

Last reported Nov 2026

Blanagram Finder

Given two strings, determine if they are blanagrams of each other. Two words are blanagrams if they have the same length and can be transformed…

Companies: Okta

Last reported Nov 2026

Bootloader Infinite Loop Detection

Given a set of bootloader instructions (Jump, Plus, Next), determine if the instruction sequence contains an infinite loop. If a loop is detected, find the…

Companies: Anthropic

Last reported Nov 2026

Course Schedule II

Given numCourses and prerequisite pairs, return any ordering of courses that satisfies all prerequisites or an empty array if impossible — this is essentially computing…

Companies: Amazon, Anduril, Apple, Citadel +11

Breadth-First Search · Depth-First Search · Graph Theory · Topological Sort

Last reported Nov 2026

Design a Battleship Game: Implement Hit, Miss, or Sunk Detection

Design a `findShip` method that takes a coordinate as input and determines whether an attack results in a hit, miss, or sunk ship. The solution…

Companies: GitHub

Last reported Nov 2026

Design a Job Processing System

Design and simulate a distributed job processing system with producers, a job coordinator, and consumers. Extend the system to support scheduled/delayed jobs and multi-tenancy…

Companies: Humaninterest

Last reported Nov 2026

Design Dasher Payout Calculation System Based on Delivery Events

Design an API/class that calculates payout for a delivery driver (Dasher) based on delivery events from an external service. Each delivery has events with timestamps…

Companies: DoorDash

Last reported Nov 2026

Design In-Memory File System

Design an in-memory hierarchical file system that supports path parsing and operations like mkdir, ls, addContentToFile (append/create), and readContentFromFile, requiring you…

Companies: Anchorage Digital, Capital One, Coupang, Datadog +5

Design · Hash Table · Sorting · String

Last reported Nov 2026

Design Snake Game

Simulate a Snake game on an m×n grid supporting move(direction): the snake advances, grows when it eats sequentially placed food (increasing score), and the game…

Companies: Apple, Atlassian, Bloomberg, Meta +1

Last reported Nov 2026

KV Store Serialize/Deserialize

Code a simple KV with serialize/deserialize functions, where key/value are strings and can contain any character.

Companies: OpenAI

Last reported Nov 2026

LFU Cache

Implement an LFU cache with O(1) average-time get and put operations that evicts the least-frequently-used key when capacity is exceeded, breaking ties by least-recently-used…

Companies: Amazon, Apple, Cisco, Goldman Sachs +3

Design · Doubly-Linked List · Hash Table · Linked List

Last reported Nov 2026

Minimize Maximum Chebyshev Distance by Adding One Delivery Center

Given an N×M city grid where delivery centers are marked as 1 and houses as 0, find the minimum possible maximum Chebyshev distance (8-directional movement)…

Companies: Amazon

Last reported Nov 2026

Minimum Remove to Make Valid Parentheses

Given a string of lowercase letters and parentheses, remove the minimum number of '(' or ')' characters so the remaining string is a valid parentheses…

Companies: Bloomberg, Meta, Microsoft

Last reported Nov 2026

Movie Recommendation System

Design and implement a movie recommendation system that suggests related or similar films based on a given input movie or user preferences. Your solution should…

Companies: Google, Intuit, Netflix

Last reported Nov 2026

Package Installation Order

Given a dependency adjacency list to install packages, return the installation order or throw an exception if a cycle is found.

Companies: Amazon, Uber

Last reported Nov 2026

Reconstruct Itinerary

Given a list of directed flight tickets, reconstruct an itinerary starting at "JFK" that uses every ticket exactly once and, among all valid itineraries, returns…

Companies: Amazon, Anduril, Google, Pinterest

Array · Depth-First Search · Eulerian Circuit · Eulerian Path

Last reported Nov 2026

Text Justification

Given an array of words and a maximum line width maxWidth, format the text so that each line has exactly maxWidth characters and is fully…

Companies: Airbnb, Amazon, Anyscale, Capital One +3

Array · Simulation · String

Last reported Nov 2026

Walls and Gates (Distance to Nearest Gate)

Given a 2D grid containing empty rooms/spaces (INF), walls/obstacles (-1), and gates (0), fill each empty room with the shortest distance to its nearest gate…

Companies: DoorDash, Microsoft, Spotify

Last reported Nov 2026

Circuit Breaker Pattern Implementation

Implement a Web API client with circuit breaker functionality that blocks requests to a service after 3 failures within 10 minutes, then reopens after a…

Companies: Databricks, Uber, Wise

Last reported Oct 2026

Design Tic-Tac-Toe

Implement a Tic-Tac-Toe class for an n×n board that supports making moves and immediately reports whether a player wins; the key challenge is designing state…

Companies: Airwallex, Amazon, Databricks, Meta +1

Last reported Oct 2026

Find Leaves of Binary Tree

Given a binary tree, simulate the process of repeatedly removing all current leaf nodes and recording their values until the tree is empty. Return a…

Companies: Amazon, eBay, Google, LinkedIn +1

Last reported Oct 2026