Rotate List

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.

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode *rotateRight(ListNode *head, int k) {
12         
13         int size = 0;
14         ListNode *p = head;
15         while(p != NULL)
16         {
17             size++;
18             p = p->next;
19         }
20         
21         if(size == 0 || size == 1)
22             return head;
23             
24         k = k % size;
25         for(int i = 0; i < k; i++)
26         {
27             ListNode *pretail = head;
28             while(pretail->next->next != NULL)
29                 pretail = pretail->next;
30                 
31             ListNode *tail = pretail->next;
32             pretail->next = NULL;
33             tail->next = head;
34             head = tail;
35         }
36         
37         return head;
38     }
39 };