Inorder tree traversal: Which definition is correct?

Question

I have the following text from an academic course I took a while ago about inorder traversal (they also call it pancaking) of a binary tree (not BST):

Answer 1

Forget the definitions, it's so much easier to just apply the algorithm:

void inOrderPrint(Node root)
{
  if (root.left != null) inOrderPrint(root.left);
  print(root.name);
  if (root.right != null) inOrderPrint(root.right);
}

It's just three lines. Rearrange the order for pre- and post- order.