private void print(Node root){
        while(root != null){
            System.out.print(root.data + " ");
            root = root.next;
        }
    }
http://www.careercup.com/question?id=6241652616200192
Test cases:
0,1 or more nodes in the tree
src/com/interview/tree/BinaryTreeToSortedLinkList.java