public Node shuffleMergeRecursive(Node head1, Node head2){
        if(head1 == null){
            return head2;
        }
        
        if(head2 == null){
            return head1;
        }
        
        Node recur = null;
        recur = shuffleMergeRecursive(head1.next, head2.next);
        
        head1.next = head2;
        head2.next = recur;
        return head1;
    }
http://www.geeksforgeeks.org/merge-a-linked-list-into-another-linked-list-at-alternate-positions/
Given two linklist shuffle merge them.
e.g head1 = {1->3->5}
head2 = {2->4}
result = {1->2->3->4->5}
Test cases
head1 is null and head2 is not
head2 is null and head1 is not
both are null
more nodes in head1 than head2
more nodes in head2 than head1
@author tusroy
src/com/interview/linklist/ShuffleMerge.java