Interview questions

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

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

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

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

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

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

Construct Quad Tree

Given an n×n binary grid (n a power of two), recursively build a quadtree by subdividing the grid into four equal quadrants until each region…

Companies: Snowflake, Uber

Array · Divide and Conquer · Matrix · Tree

Last reported May 2026

Throne Inheritance

Maintain an evolving rooted family tree (king as root) that supports adding a child and marking a person dead, and return the current inheritance order…

Companies: Apple, Snowflake

Depth-First Search · Design · Hash Table · Tree

Last reported May 2026

Binary Tree Coloring Game

Given a binary tree and the node x chosen by player 1, determine whether player 2 can pick a node y that guarantees victory by…

Companies: Anduril

Binary Tree · Depth-First Search · Tree

Last reported May 2026

Path Sum II

Find all root-to-leaf paths in a binary tree whose node values sum to targetSum, returning each path as a list of values. This is solved…

Companies: Amazon, Meta, Microsoft, Salesforce

Backtracking · Binary Tree · Depth-First Search · Tree

Last reported May 2026

Smallest Common Region

Given lists where each entry names a parent region followed by its immediate subregions and two region names, find their smallest common region — the…

Companies: Airbnb

Array · Binary Lifting · Breadth-First Search · Depth-First Search

Last reported Apr 2026

Serialize and Deserialize N-ary Tree

Design algorithms to serialize an N-ary tree into a single string and deserialize it back, preserving node values and the arbitrary number and order of…

Companies: Apple, Bloomberg, Rubrik, TikTok

Breadth-First Search · Depth-First Search · String · Tree

Last reported Mar 2026

All Nodes Distance K in Binary Tree

Given a binary tree and a target node value, return all node values at distance K from the target. The challenge is to traverse both…

Companies: Amazon, Meta, Microsoft, TikTok

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

Last reported Mar 2026

Boundary of Binary Tree

Return the boundary of a binary tree: list nodes on the left boundary top-down (excluding leaves), then all leaves left-to-right, then the right boundary bottom-up…

Companies: Amazon, Meta, Snowflake

Binary Tree · Depth-First Search · Tree

Last reported Feb 2026

Count Pairs of Connectable Servers in a Weighted Tree Network

For each node c in a weighted tree, count unordered pairs of distinct servers (a,b) (neither equal to c) such that the distances from c…

Companies: NVIDIA, Rippling

Array · Depth-First Search · Tree

Last reported Dec 2025

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

Count Nodes Equal to Average of Subtree

Count the nodes in a binary tree whose value equals the integer average (floor of sum/count) of all values in their subtree — solved by…

Companies: Meta, Snowflake

Binary Tree · Depth-First Search · Tree

Last reported Aug 2025

Binary Tree Inorder Traversal

Return the node values of a binary tree in inorder (left → root → right) sequence. The recursive solution is trivial; the follow-up asks for…

Companies: Anduril, Meta, Oracle

Binary Tree · Depth-First Search · Stack · Tree

Last reported Jul 2025

Kth Smallest Element in a BST

Return the k-th smallest value (1-indexed) in a BST — exploit that an in-order traversal yields values in sorted order and pick the k-th visited…

Companies: Amazon, Google, Meta, Uber

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

Last reported Mar 2025

Insert into a Binary Search Tree

Given a BST root and a value not already present, insert the value as a new leaf in the correct position to preserve BST ordering…

Companies: Anduril, LinkedIn

Binary Search Tree · Binary Tree · Tree

Last reported Feb 2025

Balanced Binary Tree

Check whether a binary tree is height-balanced, i.e., for every node the heights of its left and right subtrees differ by at most one. With…

Companies: Anduril

Binary Tree · Depth-First Search · Tree