Rotate List

做个circle ，看讨论来的

关键是怎么找到从哪里切，最后个循环的条件 len - k%len

public class Solution {    public ListNode rotateRight(ListNode head, int k) {        if(head==null || head.next == null ||k==0) return head;        ListNode n = head;        int len = 1;        while(n.next!=null) {            n = n.next;            len++;        }        n.next = head;        ListNode pre = n;        n = n.next;                for(int i=0; i< len-k%len; i++){            n = n.next;            pre = pre.next;        }        pre.next = null;        return n;            }}