leetcode Rotate List

class Solution {
public:
ListNode *rotateRight(ListNode *head, int k) {
if(head==NULL||k==0)
return head;

int len = 1;
ListNode* p = head;
while(p->next!=NULL)
{
p = p->next;
len++;
}

p->next = head;
int step = len - (k%len);

while(step>0)
{
p = p->next;
step--;
}

ListNode* newHead = p->next;
p->next = NULL;
return newHead;
}
};