6-6-带头结点的链式表操作集-函数题

解题代码

int Last(List L,List P) {
	int ret = 1;
	List last = L;
	while (last) {
		if (last->Next == P) {
			ret = 0;
			break;
		}
		last = last->Next;
	}
	return ret;
}
List MakeEmpty() {
	List head = (List)malloc(sizeof(struct LNode));
	head->Next = NULL;
	return head;
}
Position Find(List L, ElementType X) {
	Position ret = ERROR;
	List t = L->Next;
	while (t) {
		if (t->Data == X) {
			ret = t;
			break;
		}
		t = t->Next;
	}
	return ret;
}
bool Insert(List L, ElementType X, Position P) {
	bool flag = false;
	if (Last(L,P)) {
		printf("Wrong Position for Insertion\n");
	}
	else {
		List add = (List)malloc(sizeof(struct LNode));
		List p = L, t = p->Next;
		while (t||t==P) {
			if (t==P) {
				add->Data = X;
				add->Next = t;
				p->Next = add;
				flag = true;
				break;
			}
			p = t;
			t = t->Next;
		}
	}
	return flag;
}
bool Delete(List L, Position P) {
	bool flag = false;
	if (Last(L, P)) {
		printf("Wrong Position for Deletion\n");
	}
	else {
		List p = L, t = p->Next;
		while (t) {
			if (t == P) {
				p->Next = t->Next;
				free(t);
				flag = true;
				break;
			}
			p = t;
			t = t->Next;
		}
	}
	return flag;
}

测试结果

问题整理

1.注意如何判断调用的地址是否合法。