[LeetCode61]Rotate List

题目：

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.

分类：LinkedList   TwoPointers

代码：关键构造一个环再从相应位置断开

 /**
  * Definition for singly-linked list.
  * struct ListNode {
  *     int val;
  *     ListNode *next;
  *     ListNode(int x) : val(x), next(NULL) {}
  * };
  */
 class Solution {
 public:
     ListNode* rotateRight(ListNode* head, int k) {
         if(!head)
             return head;
         int length = ;
         ListNode *newHead, *tail;
         newHead = tail = head;
         //得到结点数
         while(tail->next)
         {
             tail = tail->next;
             length++;
         }
         //构造一个换
         tail->next = head;

         if(k %= length)
         {
             for(int i = ; i < length - k; ++i)
                 tail = tail->next;
         }
         newHead = tail->next;
         tail->next = NULL;
         return newHead;
     }
 };