template<class T>
class MyStack//链栈
{
private:
    struct StackNode
    {
        T data;
        StackNode* next;
        StackNode(const T& val = T(), StackNode* p = nullptr) :data(val), next(p) {}
        //
    };
    StackNode* top;
    int cursize;
    void clone(const MyStack& s)
    {
        Clear();
        cursize = s.cursize;
       
        StackNode* p = s.top;
        if (p == nullptr)return;
        top = new StackNode(p->data);
        StackNode* tail = top;
        p = p->next;
        while (p != nullptr)
        {
            tail=tail->next = new StackNode(p->data);
            p = p->next;
        }
    }
public:
    MyStack():cursize(0), top(nullptr) {}
    MyStack(const MyStack& s) :top(nullptr), cursize(s.cursize)
    {
        clone(s);
     }
    MyStack& operator=(const MyStack& s)
    {
        if (this != &s)
        {
           
            clone(s);
            
        }
        return *this;
    }
    ~MyStack()
    {
        Clear();
    }
    void Clear()
    {
        while (top != nullptr)
        {
            StackNode* q = top;
            top = q->next;
            delete q;
        }
        cursize = 0;
    }
    int Size()const
    {
        return cursize;
    }
    bool Empty()const
    {
        return Size() == 0;
    }
    void  Push(const T& val)//入栈
    {
        top = new StackNode(val, top);//头插
        cursize += 1;


    }
    const T& Top()const//返回栈顶元素
    {
        return top->data;
    }
    void Pop()//出栈
    {
        StackNode* q = top;
        top = q->next;
        delete q;
        cursize -= 1;

    }
    bool GetTop(T& val)//得到栈顶元素并出栈
    {
        if (Empty())return false;
        val = top->data;
        StackNode* q = top;
        top = q->next;
        delete q;
        cursize -= 1;
        return true;

    }

};

int main()
{
    MyStack<char>cmys;
    MyStack<int>imys;
    MyStack<double> dmys;

    for (char c = 'a'; c < 'z'; c++)
    {
        cmys.Push(c);
    }
    char val;
    while (cmys.GetTop(val))
    {
        cout << val << endl;
    }
    return 0;
}