我的复制构造函数弄乱了列表中的第一个元素

Question

下面是我的复制构造函数的代码，或者更确切地说是我的重载函数，但我的导师称它为复制构造函数：

void operator=(const Stack& s)
    {
        if (s.top == NULL)
            top == NULL;
        else
        {
            top = new Node;
            top->link = s.top->link;
            Node* newP = top;

                for(Node* curr = s.top->link; curr != NULL; curr = curr->link)
                {
                    newP->link = new Node;
                    newP = newP->link;
                    newP->data = curr->data;
                }
        }
    }

我希望收到的输入将与我得到的输入一起显示在下面的图像中。

据我了解，NULL 等于 0，所以我想知道我的 s.top 设置为 NULL 是否正在停止成功复制。

Answer 1

我在下面的代码中添加了我认为可以解决您的问题的注释。

void operator=(const Stack& s)
{
    if (s.top == NULL)
        top == NULL; // make sure you delete the existing nodes if there are any - this looks like a leak
    else
    {
        top = new Node; 
        top->link = s.top->link; // you need to remove this line you will allocate a new link later
        top->data = s.top->data; // this is the missing line messing with your first node
        Node* newP = top;

        for (Node* curr = s.top->link; curr != NULL; curr = curr->link)
        {
            newP->link = new Node; 
            newP = newP->link; // here's your issue - on the first iteration you're stepping over the first node but you never set the data for it
            newP->data = curr->data;
        }
    }
}