Question

Stack.h

#ifndef STACK H #define STACK H /1 your name // Stack.h // date // description #include «vector» using namespace std; template <typename T> class Stack vector<T> container; public: Stack (): container) void push (T x) container.push back(x); void pop) container.pop back); T top) t return container.back); bool empty() t return container.emptyO; b: #endif

Stack_test.cpp

What would happen if we add

s2.pop();

or

cout << s2.top();

to the end of the program (when s2 is empty?)

Fix Stack.h so that these problems would not occur.

Answer 1

If we add

s2.pop()

or

cout<<s2.top();

Then the program would crash as there would be a run time error. It is because the stack is already empty and we are trying to remove an element from an empty stack. So, it will cause a runtime error resulting into a crash of the program.

We can fix this by adding a check condition in the pop() and top() funciton.

So, the correct code is

------------------------Stack.h----------------------

#ifndef STACK_H

#define STACK_H

#include<iostream>

#include<vector>

using namespace std;

template<typename T>

class Stack

{

    vector<T> container;

   

    public:

       

        Stack(): container() {}

       

        void push(T x)

        {

            this->container.push_back(x);

        }

       

        void pop()

        {

            // if the container is not empty

            if( !this->empty() )

                this->container.pop_back();

        }

       

        T top()

        {

            // if the container is not empty

            if( !this->empty() )

                return this->container.back();

            // if the container is empty

            else

                return NULL;

        }

       

        bool empty()

       {

            return this->container.empty();

        }

};

#endif

----------------------main.cpp-------------------

#include<iostream>

#include<string>

#include "Stack.h"

int main()

{

    Stack<int> s1;

   

    s1.push(4);

    s1.push(3);

    s1.push(2);

    s1.push(1);

   

    while( !s1.empty() )

    {

        cout<<s1.top()<<endl;

        s1.pop();

    }

   

    Stack<string> s2;

   

    s2.push("Yoda said");

    s2.push("something");

    s2.push("to write");

   

    while( !s2.empty() )

    {

        cout<<s2.top();

        s2.pop();

    }

  

    cout<<endl;

   

    return 0;

}