[LeetCode] 143. Reorder List

void reorderList(ListNode* head)
{
	if(head==NULL||head->next==NULL) return;
	ListNode *l1=head,*l2=head->next;
	while(l2&&l2->next)
	{
		l1=l1->next;
		l2=l2->next->next;
	}
	ListNode *h=l1->next;
	l1->next=NULL;
	ListNode *p=h->next;
	h->next=NULL;
	while(p)
	{
		ListNode *s=p;
		p=p->next;
		s->next=h;
		h=s;
	}
	p=head;
	while(h)
	{
		ListNode *s=p->next;
		p->next=h;
		h=h->next;
		p->next->next=s;
		p=s;
	}
}