相似题型：删除链表的第倒数第n个节点，建议先做，有利于理解

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