链表复制构造函数 |未定义的行为

Question

我一直在构建一个模板链接列表，最近实现了一个用户定义的复制构造函数来处理我的链接列表的深层副本。我当前的解决方案编译得很好，但是当我执行时，什么都没有显示。

#include <iostream>

template<typename T>
class LinkedList
{
private:
    struct Node
    {
        T data;
        Node* next;
    };

    Node* head;
    Node* tail;
    int size;

public:
    LinkedList();
    LinkedList(const LinkedList<T> &list);
    ~LinkedList();
    LinkedList<T>& operator=(const LinkedList<T> list);
    int getSize() const;
    void display() const;
    void push(const T &data);
    void insert(const int pos, const T &data);
    void remove(const int pos);

};

template<typename T>
LinkedList<T>::LinkedList() : head{ nullptr }, tail{ nullptr }, size{ 0 }
{
}

// TODO: User-defined copy constructor
template<typename T>
LinkedList<T>::LinkedList(const LinkedList<T> &list)
    : head{ nullptr }, tail{ nullptr }, size{list.size}
{
    std::cout << "In the copy constructor\n";
    if (list.head == nullptr)
    {
        return;
    }
    else
    {
        Node* curNode = new Node{list.head->data, nullptr};
        head = curNode; // sets the head member variable to first node in Linked List

        Node* curListNode = list.head;      

        while (curListNode->next != nullptr)
        {
            curNode->next = new Node{curListNode->next->data, nullptr};

            curListNode = curListNode->next;
            curNode = curNode->next;
        }

        curNode->next = new Node{curListNode->next->data, nullptr};
        tail = curNode->next;
    }

}

template<typename T>
LinkedList<T>::~LinkedList()
{
    Node* prevNode = head;
    Node* curNode = head;

    while(curNode != nullptr)
    {
        prevNode = curNode;
        curNode = curNode->next;

        delete prevNode;
    }

    head = nullptr;
    tail = nullptr;
}

template<typename T>
LinkedList<T>& LinkedList<T>::operator=(const LinkedList<T> list)
{
    // make a copy of each node - much like the copy constructor
    std::cout << "In the overloaded assignment\n";
}

template<typename T>
int LinkedList<T>::getSize() const
{
    return size;
}

template<typename T>
void LinkedList<T>::display() const
{
    Node* curNode = head;

    while (curNode != nullptr)
    {
        std::cout << curNode->data << '\n';
        curNode = curNode->next;
    }

    std::cout << '\n';
}

template<typename T>
void LinkedList<T>::push(const T &data)
{
    Node* newNode = new Node{data, nullptr};

    if (size == 0)
    {
        head = newNode;
        tail = newNode;
    }
    else 
    {
        tail->next = newNode;
        tail = newNode;
    }

    ++size;
}

template<typename T>
void LinkedList<T>::insert(const int pos, const T &data)
{
    if (pos < 0 || pos > size)
    {
        throw "Index is out of range!";   
    }
    else if (pos == size)
    {
        push(data);   
    }
    else
    {
        Node* newNode = new Node{data, nullptr};
        Node* prevNode = head;
        Node* curNode = head;

        int i = 0;
        while (i != pos)
        {
            prevNode = curNode;
            curNode = curNode->next;
            ++i;
        }

        prevNode->next = newNode;
        newNode->next = curNode;

        ++size;
    }
}

template<typename T>
void LinkedList<T>::remove(const int pos)
{
    if (pos < 0 || pos > size)
    {
        throw "Index is out of range!";   
    }
    else if (size == 0)
    {
        throw "List is empty!";   
    }
    else
    {
        Node* prevNode = head;
        Node* curNode = head;

        int i = 1;
        while (i != pos)
        {
            prevNode = curNode;
            curNode = curNode->next;
            ++i;
        }

        prevNode->next = curNode->next;
        delete curNode;

        if (pos == size)
        {
            tail = prevNode;   
        }

        --size;
    }
}

int main()
{
    LinkedList<int> list;

    list.push(1);
    list.push(3);
    list.push(6);

    list.display();

    LinkedList<int> copyList{list};

    copyList.display();

    return 0;
}

当我将copyList 语句添加到main() 时，甚至不显示第一个LinkedList<int> list。但是，当我注释掉这两个 copyList 语句时，list 会正常显示。

我添加了打印语句以查看是否正在调用复制构造函数或operator= 函数，并且当copyList 语句添加到我的程序中时，它们都没有打印到控制台（代码编译得很好） .

我可以使用任何帮助来帮助诊断导致此行为的原因。

Answer 1

像这样一个简单的复制构造函数就足够了：

template<typename T>
LinkedList<T>::LinkedList(const LinkedList<T> &list)
    : head{ nullptr }, tail{ nullptr }, size{0}
{
    std::cout << "In the copy constructor\n";
   Node* curNode = list.head;

    while (curNode != nullptr)
    {
      this->push(curNode->data);
        curNode = curNode->next;
    }

}

请注意，这只是您重写的 display 方法以在当前列表中插入元素。