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;
    }
};

leetcode - Rotate List