leetcode - 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) {}
* };
*/
struct ListNode
{
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};
class Solution {
public:
ListNode *rotateRight(ListNode *head, int k) {
if(head == NULL || head->next == NULL || k == 0) return head;
ListNode *p = head,*q = NULL;
int ListNodeLength = 0;
while(p != NULL)
{
ListNodeLength++;
q = p;
p = p->next;
}
k %= ListNodeLength;
p = head;
for(int i = 0; i < ListNodeLength - k - 1; i++)
{
p = p->next;
}
q->next = head;
head = p->next;
p->next = NULL;
return head;
}
};