Interview questions

Find All Possible Recipes from Given Supplies

Given recipes whose ingredients may include other recipes and an initial set of supplies, determine which recipes can be produced; the core challenge is dependency…

Companies: Amazon, Google, Tesla

Array · Directed Acyclic Graph · Graph Theory · Hash Table

Last reported Feb 2026

Find All Anagrams in a String

Given strings s and p, return all start indices of substrings in s that are anagrams of p; the core challenge is to detect equal…

Companies: Amazon, Databricks, Microsoft

Hash Table · Sliding Window · String

Last reported Feb 2026

Design Authentication Manager

Manage tokens that expire timeToLive seconds after creation/renewal, supporting generate, renew (only if the token is still unexpired), and countUnexpiredTokens (with…

Companies: Adobe, OpenAI

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

Last reported Feb 2026

Walking Robot Simulation

Simulate a robot on an infinite grid executing turn commands and unit-step moves, stopping any step that would hit an obstacle and updating its facing…

Companies: Apple, Meta, Shopify

Array · Hash Table · Simulation

Last reported Feb 2026

Amount of Time for Binary Tree to Be Infected

Given a binary tree and a start node, compute how many minutes it takes for an infection that spreads each minute to adjacent nodes (parent/children)…

Companies: Microsoft, Salesforce

Binary Tree · Breadth-First Search · Depth-First Search · Hash Table

Last reported Dec 2025

Longest Repeating Character Replacement

Find the length of the longest substring that can be turned into all the same letter by performing at most k character replacements; this is…

Companies: D. E. Shaw, Goldman Sachs, Meta, Microsoft +1

Hash Table · Sliding Window · String

Last reported Oct 2025

Reorganize String

Rearrange the characters of a string so that no two adjacent characters are the same, returning any valid permutation or "" if none exists. Key…

Companies: Amazon, D. E. Shaw, Tesla

Counting · Greedy · Hash Table · Heap (Priority Queue)

Last reported Jan 2025

Max Points on a Line

Given up to 300 unique 2D points, return the maximum number that lie on the same straight line. The core challenge is grouping points by…

Companies: Google, LinkedIn

Array · Euclidean Algorithm · Geometry · Greatest Common Divisor

Last reported Jan 2025

Contains Duplicate

Return true if any integer appears at least twice in the array and false if all elements are distinct. Array length can be up to…

Companies: Google, Meta

Array · Hash Table · Sorting

Last reported Oct 2024

Smallest String With Swaps

Given a string and allowed index swap pairs, view pairs as edges in a graph to find connected components where characters can be freely permuted…

Companies: Goldman Sachs, Google

Array · Breadth-First Search · Depth-First Search · Hash Table

Last reported Oct 2024

Design Movie Rental System

Maintain dynamic collections to (1) return the cheapest up-to-5 shops that have an unrented copy of a given movie and (2) report the cheapest up-to-5…

Companies: Amazon, Okta

Array · Design · Hash Table · Heap (Priority Queue)

Last reported Sep 2024

Alphabet Board Path

Convert each target letter to its board coordinates and output a shortest sequence of moves (U/D/L/R) plus '!' to spell the string by walking between…

Companies: Atlassian

Hash Table · String

Avoid Flood in The City

Assign dry operations on zero days so that no lake is rained on while already full: given a sequence where rains[i]>0 fills a lake and…

Companies: MongoDB

Array · Binary Search · Greedy · Hash Table

Contiguous Array

Find the maximum length of a contiguous subarray in a binary array that contains an equal number of 0s and 1s. This is solved by…

Companies: Cisco

Array · Hash Table · Prefix Sum

Count Number of Nice Subarrays

Count the number of contiguous subarrays that contain exactly k odd numbers in an integer array. The core challenge is to do this in linear…

Companies: TikTok

Array · Hash Table · Math · Prefix Sum

Count Paths That Can Form a Palindrome in a Tree

Count pairs of nodes in a rooted tree whose path edge-letters can be rearranged into a palindrome — equivalently, the multiset of letters on the…

Companies: Goldman Sachs

Bit Manipulation · Depth-First Search · Hash Table · Tree

Count Vowel Substrings of a String

Count the number of contiguous substrings that consist only of vowels and contain all five vowels (a, e, i, o, u) at least once. The…

Companies: D. E. Shaw, Expedia, Salesforce, Snowflake

Hash Table · String

Design Ride Sharing System

Companies: Rippling

Data Stream · Design · Hash Table · Queue

Encrypt and Decrypt Strings

Implement an Encrypter that maps each character to a two-letter code and supports encrypting by replacing characters and decrypting by counting how many dictionary words…

Companies: Duolingo

Array · Design · Hash Table · String

Find All Lonely Numbers in the Array

Find all integers that occur exactly once in nums and whose immediate neighbors (x-1 and x+1) do not appear in the array; return these "lonely"…

Companies: Apple

Array · Counting · Hash Table

Fruit Into Baskets

Given an array of fruit types where you can pick from a contiguous sequence while carrying at most two distinct types (two baskets), return the…

Companies: Adobe, Amazon, Meta, Salesforce

Array · Hash Table · Sliding Window

High Five

Given a list of (studentId, score) pairs, compute each student's average of their top five scores and return the results as (studentId, average) sorted by…

Companies: Goldman Sachs

Array · Hash Table · Heap (Priority Queue) · Sorting