Intro

Linear structures. Arrays, linked lists, stacks, queues. Organize data in a line. Binary trees introduce hierarchy: each node can have two children, creating branching structure.

This branching enables logarithmic operations. A balanced binary tree with $n$ nodes has height $O(\log n)$.

Operations that traverse root-to-leaf take $O(\log n)$ instead of $O(n)$.

Trees model real problems naturally: file systems, organization charts, decision processes, expression evaluation.

Trees are the gateway to BSTs, heaps, tries, and segment trees.

In this section, I'll teach you the three traversal orders, recursive tree thinking, and construction from traversal sequences. These skills are needed for every tree-based algorithm.