将工程可扩展性融入应用程序(Engineering scalability into an application)

 前面的大事：这是一个二叉树，而不是链表。 将其称为链接列表只会导致混淆。 
 
 在主题上，递归不是链接列表的方法。 对于一棵树它可能是。 但你有什么不起作用有几个原因。 
 
 1）没有终止条件。 递归将犁入NULL指针并做坏事。 如果nodePtr为NULL，则首先在recursiveCreate中退出。 
 
 2）您正在设置当前节点以指向错误的东西。 例如， 
 
n->right = ptr->right;
 
 让节点指向错误列表中的节点。 这几乎是一个糟糕的结局。 您想指向由recursiveCreate创建的节点。 
 
 让我们来看看这将是什么样子： 
 
nodePtr LinkedList::recursiveCreate(nodePtr ptr)
{
    if (ptr == nullptr) 
    {
        return nullptr; // source tree stops here
    }
    nodePtr n = new node; //create new node
    n->elt = ptr->elt;      //copy value into that new node
    n->right = recursiveCreate(ptr->right);  //call on right node
    n->below = recursiveCreate(ptr->below);  //call on below node
    return n;
}
 
 和 
 
LinkedList::LinkedList(const LinkedList &list)
{
    nodePtr current = nullptr;

    if (list.head == nullptr) // NAG!!! For Crom's sake! 0 is not a pointer!
        head == nullptr;      // Use nullptr and get type checking working for you.

    else
    {
        head = recursiveCreate(list.head);       
    }
}
 
 特殊奖金运营商 
 
LinkedList & operator=(LinkedList list) // pass by reference. Copy constructor copies 
                                        // for you
{
    std::swap(head, list.head); // steal head from copy and give copy the empty   
    return *this; // all done.
}

The up front big thing: This is a binary tree, not a linked list. Calling it a linked list just leads to confusion. 
 
On topic, recursion is not the way to go for a linked list. For a tree it could be. But what you have does not work for a couple reasons. 
 
1) There is no terminating condition. The recursion will plow into a NULL pointer and do bad things. First off in recursiveCreate you want to exit if nodePtr is NULL. 
 
2) You're setting the current node to point at the wrong stuff. For example, 
 
n->right = ptr->right;
 
has the node pointing at a node in the wrong list. That's an almost certain bad end. You want to point at the node created by recursiveCreate. 
 
Let's take a look at what this would have to look like:
 
nodePtr LinkedList::recursiveCreate(nodePtr ptr)
{
    if (ptr == nullptr) 
    {
        return nullptr; // source tree stops here
    }
    nodePtr n = new node; //create new node
    n->elt = ptr->elt;      //copy value into that new node
    n->right = recursiveCreate(ptr->right);  //call on right node
    n->below = recursiveCreate(ptr->below);  //call on below node
    return n;
}
 
and 
 
LinkedList::LinkedList(const LinkedList &list)
{
    nodePtr current = nullptr;

    if (list.head == nullptr) // NAG!!! For Crom's sake! 0 is not a pointer!
        head == nullptr;      // Use nullptr and get type checking working for you.

    else
    {
        head = recursiveCreate(list.head);       
    }
}
 
Special bonus operator
 
LinkedList & operator=(LinkedList list) // pass by reference. Copy constructor copies 
                                        // for you
{
    std::swap(head, list.head); // steal head from copy and give copy the empty   
    return *this; // all done.
}