Interview questions

Longest Cycle in a Graph

Given a functional directed graph (each node has at most one outgoing edge), return the length of the longest directed cycle or -1 if no…

Companies: Anduril

Breadth-First Search · Depth-First Search · Graph Theory · Kosaraju's Algorithm

Last reported Oct 2026

Cheapest Flights Within K Stops

Find the minimum-cost route from src to dst in a directed weighted graph with the constraint of at most k stops (i.e., a bound on…

Companies: Flipkart, Illumio, Meta, Oracle +1

Breadth-First Search · Depth-First Search · Dynamic Programming · Graph Theory

Last reported Oct 2026

Course Schedule

Given courses as nodes and prerequisite pairs as directed edges, determine whether the directed graph is acyclic — return true if a topological ordering exists…

Companies: Amazon, Anduril, Cloudflare, DoorDash +6

Breadth-First Search · Depth-First Search · Directed Acyclic Graph · Graph Theory

Last reported Oct 2026

Lowest Common Ancestor of a Binary Tree

Given a binary tree and two nodes p and q, find their lowest common ancestor (LCA) — the deepest node that has both p and…

Companies: Amazon, Apple, Atlassian, Canva +6

Binary Lifting · Binary Tree · Depth-First Search · Lowest Common Ancestor

Last reported Sep 2026

Number of Islands

Count the number of islands (4-directionally connected components of '1's) in an m×n binary grid. This is a connected-components/flood-fill problem typically solved with…

Companies: Amazon, Anduril, Apple, ByteDance +16

Array · Breadth-First Search · Depth-First Search · Matrix

Last reported Sep 2026

Flatten a Multilevel Doubly Linked List

Companies: Adobe, Amazon, Bloomberg, Microsoft

Depth-First Search · Doubly-Linked List · Linked List

Last reported Sep 2026

Diameter of Binary Tree

Given the root of a binary tree, return the diameter — the maximum number of edges on any path between two nodes; the core challenge…

Companies: Meta, Oracle, Roblox

Binary Tree · Depth-First Search · DP on Trees · Tree

Last reported Sep 2026

Closest Binary Search Tree Value II

Given a BST, a real-valued target and an integer k, return the k node values in the tree closest to the target. The challenge is…

Companies: Amazon, LinkedIn

Binary Search Tree · Binary Tree · Depth-First Search · Heap (Priority Queue)

Last reported Sep 2026

Evaluate Division

Given pairwise variable ratios, build a weighted graph (or use union-find with multiplicative weights) where edges represent divisions, and answer each query by finding a…

Companies: Amazon, Bloomberg

Array · Bellman–Ford Algorithm · Breadth-First Search · Depth-First Search

Last reported Sep 2026

Alien Dictionary

Given a sorted list of words in an unknown alphabet, infer the relative ordering of characters by deriving precedence constraints between first differing letters, then…

Companies: Amazon, Bloomberg, Google, Intuit +3

Array · Breadth-First Search · Depth-First Search · Directed Acyclic Graph

Last reported Aug 2026

Number of Provinces

Given an n x n symmetric adjacency matrix where isConnected[i][j]=1 denotes a direct undirected edge between cities, count the number of connected components (provinces) formed…

Companies: Amazon, Coupang, Uber

Breadth-First Search · Depth-First Search · Graph Theory · Union-Find

Last reported Aug 2026

Binary Tree Cameras

Place the minimum number of cameras on nodes of a binary tree so every node is monitored by a camera on itself, its parent, or…

Companies: Amazon, D. E. Shaw

Binary Tree · Depth-First Search · DP on Trees · Dynamic Programming

Last reported Aug 2026

Validate Binary Search Tree

Determine whether a binary tree is a valid binary search tree by checking that each node's value is strictly greater than all values in its…

Companies: Amazon, Lyft, Microsoft

Binary Search Tree · Binary Tree · Depth-First Search · Tree

Last reported Aug 2026

Accounts Merge

Given lists of accounts where each account has a name and emails, merge accounts that share any email by grouping connected emails (e.g., via union-find…

Companies: Airbnb, Bloomberg, Meta, Oracle +1

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

Last reported Aug 2026

Flatten Nested List Iterator

Given a nested list where elements may be integers or sublists, implement a NestedIterator with next() and hasNext() that returns all integers in depth‑first, left‑to‑right…

Companies: Adobe, LinkedIn

Depth-First Search · Design · Iterator · Queue

Last reported Aug 2026

Word Search

Determine whether a target word can be formed by a path of horizontally or vertically adjacent cells in an m×n letter grid without reusing a…

Companies: Amazon, Glean, Google, Grammarly +3

Array · Backtracking · Depth-First Search · Matrix

Last reported Jul 2026

Maximum Depth of Binary Tree

Given the root of a binary tree, return its maximum depth — the number of nodes along the longest root-to-leaf path. This classic easy problem…

Companies: Google, LinkedIn

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

Last reported Jun 2026

Minimum Edge Reversals So Every Node Is Reachable

Given a directed graph whose underlying undirected graph is a tree, compute for every node the minimum number of edge reversals required so that starting…

Companies: Microsoft, Salesforce, Uber

Breadth-First Search · Depth-First Search · Dynamic Programming · Graph Theory

Last reported Jun 2026

Binary Tree Maximum Path Sum

Find the maximum sum of any non-empty connected path in a binary tree (nodes used at most once), where the path can start and end…

Companies: Amazon, Datadog, DoorDash, Expedia +4

Binary Tree · Depth-First Search · DP on Trees · Dynamic Programming

Last reported Jun 2026

Number of Distinct Islands

Given a binary grid, count how many distinct island shapes (connected components of 1s via 4-directional adjacency) appear, treating two islands as identical if they…

Companies: Anduril, Oracle, TikTok

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

Last reported Jun 2026

Closest Binary Search Tree Value

Given a Binary Search Tree and a target numeric value, return the value of the node in the tree that is closest to the target…

Companies: Expedia, Meta, Roblox

Binary Search · Binary Search Tree · Binary Tree · Depth-First Search

Last reported Jun 2026

Minesweeper

Simulate a Minesweeper click on an m×n board: clicking a mine turns it to 'X', while clicking an empty square requires counting adjacent mines —…

Companies: Meta, Microsoft, Nuro, Uber

Array · Breadth-First Search · Depth-First Search · Matrix

Last reported Jun 2026