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;
}
};