12.7 The BinaryTree class is a recursive data structure, unlike the List class. Describe how the List class would be different if it were implemented as a recursive data structure. 12.8 The parent reference in a BinaryTree is declared protected and is accessed through the accessor methods parent and setParent. Why is this any different than declaring parent to be public.

def to tree (obj: Union [int, List])-> Optional [Tree]: """Return the Tree which represents. Return None if is not a valid representation of a Tree. You may not access Tree attributes directly, since they're private. This function can be implemented only using the Tree initializer. >>> t = to_tree ([1, [2, [5], [6]], [3, [7], [8, [10]]], [4, [9]]]) >>> t._root 1 >>> t._subtrees [0]._root 2 >>> t._subtrees [1]._root 3 >>> t._subtrees [2]._root 4

24. Add the following new method in the BST class. /** Returns the number of nodes in this binary tree */ public int getNumberofNodes () Requirements: a. Don't use return size; b.write a recursive method that returns the number of nodes starting from www the root.

10.14 A CircularList is used in the implementation of QueueLists. Use Node with a head and tail reference to implement QueueLists in a time and space efficient manner. 10.15  Burger Death must keep track of all orders placed through the drive-through window. Create a data structure to help their ordering system.