Binary Tree Intro

A tree is a hierarchical structure. Real examples: - file system folders - HTML DOM - organization charts ## Tree vocabulary - root: top node - child: below a node - leaf: node with no children ## Simple binary tree node ```python class Node: def __init__(self, value, left=None, right=None): self.value = value self.left = left self.right = right ``` ## Build a small tree ```python root = Node(1, Node(2), Node(3)) ``` ## DFS traversal (in-order) ```python def inorder(node): if not node: return inorder(node.left) print(node.value) inorder(node.right) inorder(root) # 2,1,3 ``` ## BFS traversal (level order) ```python from collections import deque def bfs(root): q = deque([root]) while q: node = q.popleft() print(node.value) if node.left: q.append(node.left) if node.right: q.append(node.right) bfs(root) # 1,2,3 ``` ## Graph: tree structure ```mermaid flowchart TD A[1] --> B[2] A --> C[3] ``` ## Remember - Trees model hierarchy - DFS uses recursion or stack - BFS uses queue