Let us code the following three source files in C++: • StringList.h – In this fi

Question

Let us code the following three source files in C++:

• StringList.h

– In this file, you declare a class named StringList.

– StringList is a modified version of NumberList class (Chapter 17), that is designed to store C++ strings in a linked list.

– Therefore, each node must store a string, not a number.

– The node structure must be declared within class, and a private attribute head points to the starting node.

– The class provides a default constructor that creates an empty linked list, and a destructor that releases all the nodes.

– The class also provides public member functions for inserting and deleting a node (see below for details).

– It also provides a public member function for displaying the list.

• StringList.cpp

– In this file, you provide definitions for the default constructor and the destructor for StringList.

– Make sure the destructor visits every node in the list and deletes every one of them from the heap.

– Define insertFront function to insert a new node into the front of the list. Therefore, the new node will be the new first node in the list. This function takes a string as a parameter.

– Define insertBack function to insert a new node into the back of the list. Therefore, the new node will be the new last node in the list. This function takes a string as a parameter.

– Define deleteFront function to delete the first node from the list. This function takes no parameter.

– Define deleteBack function to delete the last node from the list. This function takes no parameter.

– Define display function that displays the current contents (strings) of the list (display strings in a single line, separated by a space). This function takes no parameter.

• hw5.cpp

– In this file, you define main function that tests StringList class.

– You must first create a StringList object. 1

– Then start inserting new nodes, one at a time. Alternate between inserting into the front and into the back. Make sure to add at least 6 nodes.

– Then start deleting nodes, one at a time. Alternate between deleting from the front and from the back.

– Make sure all the nodes are deleted before terminating the program.

– After each insertion or deletion, call display member function to display the updated list.

– Make sure all the member functions are tested and shown to work properly, without missing any of them.

– Note that the display function must be called pretty much every time a node is inserted or deleted. Otherwise the respective functionality will not be properly demonstrated and could lead to loss of points.

– Also note that each member function should properly work regardless of the current list configuration (empty list, one-node list, or multiple-node list).

Explanation / Answer

YOU CAN UNCOMMENT THE PRINT STATEMENT LINES TO UNDERSTAND THE FLOW OF PROGRAM

(En =Enter    Ex=Exit)

------------------------------------------------------------------------------------------------------------------------------------------------------------------------

StringList.h

class StringList
{
private:
  struct node
  {
   char string_val[20];
   struct node *next;
  };
  struct node *head;
  struct node *tail;
  
  void display()
  {
   //cout<<" ....En display.... ";
   struct node *trav=head;
   while(trav!=NULL)
   {
    cout<<" "<<trav->string_val;
    trav=trav->next;
   }
   if(head==NULL)
   {
    cout<<" List is Empty ";
   }

cout<<endl;
   //cout<<" ....Ex display.... ";
  }
public:
  StringList();
  void delete_front();
  
  void delete_last();
  
  void insert_front(struct node *new1);
  
  void insert_last(struct node *new1);
  struct node *new_node()
  {
   //cout<<" ....En new_node.... ";

   struct node *new1=(struct node *)malloc(sizeof(struct node));
   
   cout<<" Enter string for new node:";
   cin>>new1->string_val;
   new1->next=NULL;
   //cout<<" ....Ex new_node.... ";
   return new1;
   
   
  }
  
  ~StringList();
};

------------------------------------------------------------------------------------------------------------------------------------------------------------------------

StringList.cpp

StringList::StringList()
{
head=tail=NULL;
}
void StringList::delete_front()
{
//cout<<" ....En delete_front.... ";

if(head)
{
  struct node *temp=head;
  head=head->next;
  free(temp);
  display();
}
else
{
  cout<<" List is empty..!!!";
}
//cout<<" ....Ex delete_front.... ";
}
void StringList::delete_last()
{
//cout<<" ....En delete_last.... ";

if(head)
{
  struct node *sec_last=head;
  if(head->next!=NULL)
  {
   while(sec_last->next->next!=NULL)
   {
    sec_last=sec_last->next;
   }
  }
  
  if(sec_last->next==NULL)//if only one node in the list
  {
   free(head);
   tail=head=NULL;
  }
  else
  {
   struct node *temp=sec_last->next;
   sec_last->next=NULL;
   free(temp);
  }
  display();
}
else
{
  cout<<" List empty..!!!";
}

//cout<<" ....Ex delete_last.... ";
}
void StringList::insert_front(struct node *new1)
{
//cout<<" ....En insert_front.... ";

if(head)
{
  new1->next=head;
  head=new1;
}
else
{
  head=tail=new1;
  
}
display();

//cout<<" ....Ex insert_front.... ";
}
void StringList::insert_last(struct node *new1)
{
//cout<<" ....En insert_last.... ";

if(head==NULL)
{
  head=tail=new1;
}
else
{
  tail->next=new1;
  tail=new1;
}
display();

//cout<<" ....Ex insert_last.... ";
}
StringList::~StringList()
{
//cout<<" ....En ~StringList.... ";
while(head!=NULL)
{
  cout<<" delete ";
  delete_front();
}
//cout<<" ....Ex ~StringList.... ";
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------

hw5.cpp

#include<iostream>
#include<stdlib.h>
#include<stdio.h>
using namespace std;
#include"StringList.h"
#include"StringList.cpp"
int main()
{
StringList object;
cout<<" ----------------------------------- | Insertion Start | ----------------------------------- ";
object.insert_front(object.new_node());
object.insert_last(object.new_node());
object.insert_front(object.new_node());
object.insert_last(object.new_node());
object.insert_front(object.new_node());
object.insert_last(object.new_node());
cout<<" ----------------------------------- | Deletion Start | ----------------------------------- ";
object.delete_front();
object.delete_last();
object.delete_front();
object.delete_last();
object.delete_front();
object.delete_last();
}

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