Given the root of a binary tree
root. Return the node values in depth-first inorder traversal: left — root — right.Example 1
Input: root = [1,null,2,3]
Output: [1,3,2]
Explanation: Inorder traversal: first the left subtree, then the root, then the right.
Output: [1,3,2]
Explanation: Inorder traversal: first the left subtree, then the root, then the right.
Example 2
Input: root = [1,2,3,4,5,null,8,null,null,6,7,9]
Output: [4,2,6,5,7,1,3,9,8]
Explanation: The sequence is obtained by a standard inorder traversal of the tree.
Output: [4,2,6,5,7,1,3,9,8]
Explanation: The sequence is obtained by a standard inorder traversal of the tree.