Introduction

Why Trees?

Trees are the most important data structure beyond arrays and linked lists. They appear everywhere in software:

  • File systems — directories are trees. Every ls you run traverses one.
  • The DOM — every webpage is a tree of HTML elements.
  • Compilers — source code is parsed into an Abstract Syntax Tree (AST) before execution.
  • Databases — B-trees power the indexes that make SQL queries fast.
  • Git — the commit graph is a tree (actually a DAG). Every git log traverses it.
  • DNS — the domain name system is a tree. com → example → www.

Understanding trees is the gateway to understanding how real systems work at depth.

Why C?

Implementing trees in C forces you to understand them at the lowest level:

  • There is no garbage collector. You call malloc to create a node, and you own that memory.
  • There is no tree library. You write the struct, the insert, the traversal — everything.
  • The pointer manipulation is explicit. root->left = new_node(val) is not hidden behind an object system.

When you implement a BST in C, you understand what Python's dict and Java's TreeMap are doing under the hood.

What You Will Learn

This course contains 12 lessons organized into 4 chapters:

  1. Binary Trees — Define the Node struct, create nodes with malloc, and implement all three classic traversals: inorder, preorder, and postorder.
  2. Tree Properties — Recursive algorithms to count nodes, measure height, and count leaves.
  3. Binary Search Tree — Insert values, search for values, and find min/max using the BST property.
  4. BST Operations — Validate that a tree is a correct BST using the min-max technique.

Each lesson explains the concept, walks through the algorithm, and gives you a function to implement and test.

Let's build trees.

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