Implement inorder traversal

Summary

Implement inorder (left-root-right) traversal for a binary tree, returning the visited node values as a list.

Problem statement

Given the root of a binary tree, implement a function inorder(root) that returns a list of node values visited in inorder (left, root, right). Use the provided Node class. Handle an empty tree by returning an empty list.

Task

Write inorder(root) to traverse left subtree, visit root, then right subtree, returning list of values.

Examples

Input format

A single argument: root (Node or None).

Output format

A list of integers representing node values in inorder order.

Constraints

Tree size up to 10^4. Use recursion or iteration. Do not print; return the list.

Samples