题目链接

class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if(head == null) return null;
        int len = 1;
        ListNode tail = head;
        while(tail.next != null){
            len++;
            tail = tail.next;
        }//此刻tail已经是尾节点了

        // 3 - 4%3 = 2
        k = len-k%len;
        if(k==0) return head;

        //首尾相连
        tail.next = head;
        //1>=0 0>=0
        while(--k>=0){
            tail = tail.next;
        }
        
        head = tail.next;
        tail.next = null;
        return head;
    }
}