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.

/**
 * 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) {
        
        int size = 0;
        ListNode *p = head;
        while(p != NULL)
        {
            size++;
            p = p->next;
        }
        
        if(size == 0 || size == 1)
            return head;
            
        k = k % size;
        for(int i = 0; i < k; i++)
        {
            ListNode *pretail = head;
            while(pretail->next->next != NULL)
                pretail = pretail->next;
                
            ListNode *tail = pretail->next;
            pretail->next = NULL;
            tail->next = head;
            head = tail;
        }
        
        return head;
    }
};