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.

思路：双指针

代码：

ListNode *rotateRight(ListNode *head, int k) {
        ListNode *p=head;
        if(p == NULL)
{
return p;
}
int len=0;
while(p != NULL)
{
p=p->next;
++len;
}
if(k>=len)
{
k=k%len;
}
if(k == 0)
{
return head;
}
else
{
p=head;
ListNode *q=head;
int i=0;
while(i<k)
{
q=q->next;
++i;
}
while(q->next!=NULL)
{
q=q->next;
p=p->next;
}
ListNode *newHead=p->next;
p->next=NULL;
q->next=head;
return newHead;
}
    }