双向链表的插入

linklist insert(Node* L, int locate, int val) {
	Node* s;
	s = L->next;
	
	//加，判断locate是否大于链表的长度
	while (s->next != NULL ) {
		locate--;
		if (locate == 0) {
			break;
		}
		s = s->next;

		
	}
	//当计数器从0开始时，计数器的值比要插入的位置多1
	//
	printf("%d  %d", locate,s->val);
	//p插入的位置是 头or尾or之间；
	Node* p;
	p = (Node*)malloc(sizeof(Node));
	p->next = NULL;
	p->prev = NULL;
	p->val = 5;
	p->prev = s->prev;
	s->prev->next = p;
	p->next = s;
	s->prev = p;

	


	return L;
}