Having binary node (data, left, right) we need to implement two methods binary search tree methods:

• insert - accepts an argument data, then create an insert a new node at the appropriate location in the tree.
• contains - accepts a data argument and return the true if node with given value already exists in the tree, otherwise returns false

Requirements that are always true for any given node in Binary Search Tree:

• parent node value is always greater then value of all nodes in the left subtree
  and less than value of all nodes in the right subtree
• left node value is also a valid BST
• right node value is also a valid BST

Challenge | Solution

Example 1

val tree = Node(1)
tree.insert(4)
tree.insert(2)

// Result
//
//    1
//   / \
//  2   4

Example 2

val tree = Node(1)
tree.insert(4)
tree.insert(2)
tree.contains(4) // true
tree.contains(99) // false