Question

C++ ONLY -- PRACTICE ASSIGNMENT

We are given a code (Driver.cpp) and asked to create a file (StringStack.h) and turn it in.

What should the code for StringStack.h look like based on the instructions below?

1. Download Driver.cpp
   
2. Create a class named StringStack in a file named StringStack.h.
   
3. Create a ListNode structure as a private member of the class. The node should be able to hold a string called value.  
   
4. Create a top pointer as private attributes of the class. (this is like the head pointer for a linked list)
   
5. Create the following public member functions:
   1. A constructor, which will set top to NULL.
   2. A push function, which will push a string on top of the stack.
   3. A pop function, which will remove & return the string from the top of the stack

6. Test your stack class using the Driver.cpp file provided for you.

GIVEN DRIVER.CPP FILE:

#include <iostream>

#include "StringStack.h"

using namespace std;

int main()

{

// Define a StringStack object.

StringStack stack;

string animal, lastAnimal;

//get input from user and push to the stack

cout << "\n\nWhat did the old lady eat first? ";

getline(cin, animal);

stack.push(animal);

for(int x=0; x < 6; x++)

{

cout << "\nWhat did she eat next? ";

getline(cin, animal);

stack.push(animal);

}

cout << "\nWhat did she eat last? ";

getline(cin, animal);

stack.push(animal);

//start popping from stack and print results

lastAnimal = stack.pop();

animal = stack.pop();

cout << "\n\nShe swallowed the " << animal << " to catch the ";

animal = stack.pop();

cout << animal << ",\nShe swallowed the " << animal << " to catch the ";

animal = stack.pop();

cout << animal << ",\nShe swallowed the " << animal << " to catch the ";

animal = stack.pop();

cout << animal << ",\nShe swallowed the " << animal << " to catch the ";

animal = stack.pop();

cout << animal << ",\nShe swallowed the " << animal << " to catch the ";

animal = stack.pop();

cout << animal << "\nThat wriggled and jiggled and tickled inside her!\n";

cout << "She swallowed the " << animal << " to catch the ";

animal = stack.pop();

cout << animal << ";\nI don\'t know why she swallowed a " << animal;

cout << " - Perhaps she\'ll die!\n\n";

cout << "There was an old lady who swallowed a " << lastAnimal;

cout << ";\n...She\'s dead, of course!\n\n";

return 0;

}

Answer 1

Code to be pasted in stringStack.h

#pragma once
#include"string"
using namespace std;
class StringStack
{
private:
        struct ListNode
        {
                string str;
                ListNode *next;
        };
        ListNode *headPtr;
public:
        StringStack()
        {
                headPtr = NULL;
        }

        void push(string inp)
        {
                ListNode *temp = new ListNode; /*create a node of type list node and initialize its str*/
                temp->str = inp;
                temp->next = headPtr;  /* insert at beginning of list*/
                headPtr = temp; 
        }

        string pop()
        {
                if (headPtr == NULL) /* if stack is empty return empty string*/
                {
                        return "";
                }
                ListNode * temp = headPtr;
                headPtr = headPtr->next;   /* advance headptr to next node to delete the first node*/
                string tempStr = temp->str;  /* store string in node to tempStr. It is done to return it*/
                delete temp;  /* release memory using delete*/
                return tempStr;
        }
};