Walkthrough
How Trees Work
Step-by-step from basic structure to advanced operations
Tree Structure
A tree is a hierarchical data structure with a root node, branches, and leaves. Each node has a value and references to child nodes. Binary trees have at most 2 children per node.
Complexity
Properties
Node Colors
Practice
Interview Questions
Common questions from top company interviews
Design an auto-complete system that handles 100k searches per second using a trie.
Store search frequencies at each trie node; for a prefix, traverse to node then BFS/DFS to collect top-k words by frequency.
How would you serialize and deserialize a binary tree for storage or transmission?
Use level-order traversal with a sentinel marker (e.g., #) for null nodes; deserialize by rebuilding left/right children in queue order.
Find the lowest common ancestor of two nodes in a BST efficiently.
Traverse from root: if both nodes are greater, go right; if both smaller, go left; else the current node is the LCA.
Given a sorted array of 10k unique integers, build a height-balanced BST in O(n).
Pick the middle element as root, recursively build the left subtree from the left half and right subtree from the right half.
Coding Challenge
Practice on Terminal
Write and submit your solution, then check achievements
Design an algorithm to serialize a binary tree into a string and deserialize the string back into the original tree structure. Use level-order (BFS) serialization with "null" markers for missing nodes.