Revise previous questions asked in the Mock Interviews

[sinhaaman]

1. Insert an element in the sorted circular linked list. http://collabedit.com/q38j3
2. Reverse pairs in the doubly linked lists.
3. Reverse pairs in the singly linked list http://collabedit.com/nrmgy
4. Rotate a doubly linked list. http://collabedit.com/bauab