Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.
输入
Given this linked list: 1->2->3->4->5 For k = 2
输出
you should return: 2->1->4->3->5
样例
| 标准输入 复制文本 |
1->2->3->4->5 k=3 |
| 标准输出 复制文本 |
3->2->1->4->5 |
提示
按照每 K 个元素翻转的⽅式翻转链表。如果不满⾜ K 个元素的就不翻转。