Problem:
Convert binary search tree to doubly linked list

Solution:
– Traverse InOrder
– Keep TailPointer
– And update following things for each root
– – root.left = tail
– – tail.right = root
– – tail = root

Latest Source Code:
Github: BinarySearchTreeToDoublyLinkedList.java

Output:

        6               
      / \       
     /   \      
    /     \     
   /       \    
   -13       14       
    \     / \   
     \   /   \  
     -8   13   15   
        /       
        7       
                                

Forward: -13 -8 6 7 13 14 15 
Backward: 15 14 13 7 6 -8 -13