package leetcode._61_;

import leetcode.common.ListNode;

/**

* Definition for singly-linked list.

* public class ListNode {

* int val;

* ListNode next;

* ListNode(int x) { val = x; }

* }

*/

class Solution {

public ListNode rotateRight(ListNode head, int k) {

if (head == null || head.next == null) {

return head;

}

int length = 0;

ListNode index = head;

while (index.next != null) {

length++;

index = index.next;

}

length++;

index.next = head; // 构建成循环链表，index 指向 head 的前一个节点

k = k % length;

for (int i = 0; i < length - k; i++) {

index = head;

head = head.next;

}

index.next = null; // 破除循环链表，添加结束 null 值

return head;

}

}