请教这样释放内存的析构函数有效吗

class List
{
    public:
        List();
        ~List();
               。。。。

    private:
        Node* Listhead;
        Node* Current_Pos;
        int X;
};


List::List()
{
        Listhead=0;
    Current_Pos=0;
}

List::~List()
{

    Node* ptr = new Node;
    ptr = Current_Pos;
    while(Current_Pos!=0)
        {
        Current_Pos = Current_Pos->the_rest;
        delete ptr;
        ptr = Current_Pos;
        }
    delete Listhead;
    delete Current_Pos;
}