In this problem, please implement a binary search tree (BST).
You have to implement the following methods:
(1) Insert x:
Insert an integer x into the BST if x hasn’t in the BST yet.
(2) Size x:
Find the node x in the BST and print the number of nodes in this subtree.
If x isn't in the BST, print -1.
For each subproblem:
(1) 1416: N <= 200
(2) 1417: N <= 10000
(3) 1418: N <= 60000
N is the number of nodes in the tree.