栈

template<class Elem>
class AStack:public Stack<Elem>       //数组实现的栈类
{
private:
    int size;
    int top;
    Elem *listArray;
public:
    AStack(int sz=DefaultListSize)
    {
        size=sz;top=0;listArray=new Elem[sz];
    }
    ~AStack()
    {
        delete [] listArray;
    }
    void clear()
    {
        top=0;
    }
    bool push(const Elem& item)
    {
        if(top==size) return false;
        else
        {
            listArray[top++]=item;
        }
    }
    bool pop(Elem & it)
    {
        if(top==0) return false;
        else
        {
            it=listArray[--top];
            return true;
        }
    }
    bool topValue(Elem & it) const
    {
        if(top==0) return false;
        else
        {
            it=listArray[top-1];
            return true;
        }
    }
    int length() const 
    {
        return top;
    }
};



#include "LList.h"
template<class Elem>
//用链表实现的栈
class LStack:public Stack<Elem>
{
private:
    Link<Elem> * top;
    int size;
public:
    LStack(int sz=DefaultListSize)
    {
        top=NULL;size=0;
    }
    ~LStack()
    {
        clear();
    }
    void clear()
    {
        while(top!=NULL)
        {
            Link<Elem> *temp=top;
            top=top->next;
            size=0;
            delete temp;
        }
    }
    bool push(const Elem& item)
    {
        top=new Link<Elem>(item,top);
        size++;
        return true;
    }
    bool pop(Elem & it)
    {
        if(size==0) return false;
        it=top->element;
        Link<Elem> * ltemp=top->next;
        delete top;
        top=ltemp;
        size--;
        return true;
    }
    bool topValue(Elem &it) const
    {
        if(size==0) return false;
        it=top->element;
        return true;
    }
    int length() const
    {
        return size;
    }
};