Given the root of a binary tree, return the inorder traversal of its nodes' values. Pattern focus: Inorder DFS (Left Root Right). Visit the left subtree, then the node, then the right subtree.
root = binary tree root
inorder traversal as an array of node values
Example 1:
Input:
root = [1,null,2,3]
Output:
[1,3,2]
Explanation:
Inorder visits left subtree, root, then right subtree.
Example 2:
Input:
root = [1,2,3,4,5,null,6]
Output:
[4,2,5,1,3,6]
Explanation:
The traversal follows left-root-right order.