Given a list, rotate the list to the right by k places, where k is non-negative.
For example:Given 1->2->3->4->5->NULL and k = 2,return 4->5->1->2->3->NULL.
1->2->3->4->5->NULL
2
4->5->1->2->3->NULL
将一个链表的元素分步从后向前移动
原文：http://www.cnblogs.com/yangscode/p/5030910.html
