题目来源：https://leetcode.com/problems/rotate-list/
问题描述
61. Rotate List
Medium
Given a linked list, rotate the list to the right by k places, where k is non-negative.
Example 1:
Input: 1->2->3->4->5->NULL, k = 2
Output: 4->5->1->2->3->NULL
Explanation:
rotate 1 steps to the right: 5->1->2->3->4->NULL
rotate 2 steps to the right: 4->5->1->2->3->NULL
Example 2:
Input: 0->1->2->NULL, k = 4
Output: 2->0->1->NULL
Explanation:
rotate 1 steps to the right: 2->0->1->NULL
rotate 2 steps to the right: 1->2->0->NULL
rotate 3 steps to the right: 0->1->2->NULL
rotate 4 steps to the right: 2->0->1->NULL
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题意
给定链表和整数k，求该链表第k次旋转后的新链表。定义链表的一次旋转为将链表尾变为新的链表头，把原有链表头到链表尾的部分附在最后。
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思路
首先求链表长度L，然后k = k%L，避免产生循环计算。然后找到k次旋转之后的新链表头和新链表尾，按照旋转的定义改变链表指针即可。
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代码