C++实现栈

///2014-09-04

///author txh

#include <iostream>

using namespace std;

template <class T>

struct Node

{

    Node<T> *next;

T data;

};

template <class T>

class stack

{

public:

stack()

{

        head = new Node<T>;

        if(NULL == head)

        {

            cout<<"new head error"<<endl;

}

else

{

            head->next = NULL;

head->data = NULL;

}

}

~stack()

{

        delete head;

}

    void push(T elem)

    {

        Node<T> *p = new Node<T>;

if(NULL == p)

{

            cout<<"new Node error"<<endl;

}

else

{

            p->data = elem;

p->next = head->next;

head->next = p;

}

}

T pop()

{

   T elem;

        Node<T> *p = head->next;

if(p!=NULL)

{

elem = p->data;

head->next = p->next;

delete p;

p = NULL;

}

else

{

            cout<<"This stack is NULL"<<endl;

return NULL;

}

return elem;

}

T top()

{

        T elem;

Node<T> *p = head->next;

if(p != NULL)

{

            elem = p->data;

return elem;

}

else

{

            cout<<"This stack is NULL"<<endl;

return NULL;

}

}

int stackSize()

{

        int size = 0;

Node<T> *p = head->next;

while(p != NULL)

{

            p = p->next;

size++;

}

return size;

}

bool judgeEmpty()

{

        Node<T> *p = head;

if(p->next == NULL)

{

            return true;

}

else

{

            return false;

}

}

private:

Node<T> *head;

};

int main(int argc,char *argv[])

{

    int i=0;

    stack<int> S;

S.push(100);

S.push(200);

S.push(300);

cout<<"the top:"<<S.top()<<endl;

cout<<"the size:"<<S.stackSize()<<endl;

if(S.judgeEmpty())

{

        cout<<"this empty"<<endl;

}

else

{

         cout<<"this isn't empty"<<endl;

}

for(i=0; i<3; i++)

{

   S.pop();

        cout<<"the top:"<<S.top()<<endl;

   cout<<"the size:"<<S.stackSize()<<endl;

}

return 0;

}