LeetCode Merge Two Sorted Lists

2013年最后一天做题好顺呀

ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
	if(l1==NULL)
		return l2;
	if(l2==NULL)
		return l1;
	ListNode *p=l1;
	ListNode *q=l2;
	ListNode *head=NULL,*s=NULL;
	while(p&&q)
	{
		if (p->val<=q->val)
		{
			if (s==NULL)
			{
				head = p;
				s = head;
				p = p->next;
			}
			else
			{
				s->next = p;
				s = s->next;
				p = p->next;
			}
		}
		else
		{
			if (s==NULL)
			{
				head = q;
				s = head;
				q = q->next;
			}
			else
			{
				s->next = q;
				s = s->next;
				q = q->next;
			}
		}
	}
	if(p)
		s->next = p;
	if(q)
		s->next = q;
	if(!p&&!q)
		s->next = NULL;
	return head;
}