// My error checking is not working and I have been unable to figure out why? //

ID: 3567298 • Letter: #

Question

// My error checking is not working and I have been unable to figure out why?

//driver.cpp

#include "List.h"
#include <iostream>

using namespace std;

int main(int argc, char const *argv[])
{
   List Test;
   Test.insert("AAA", 0);
   Test.insert("BBB", 1);
   Test.insert("CCC", 2);
   Test.display(cout);
   cout << Test.getSize() << endl;

   List Test_Second;

   Test_Second = Test;

Test_Second.display(cout);
cout << Test_Second.getSize() << endl;

Test_Second.insert("DDD", 3);

List Test_Third(Test_Second);

Test_Third.display(cout);
cout << Test_Third.getSize() << endl;

system ("pause");
return 0;
}
//------------------------------------------------------------------------
//List.cpp

#include "List.h"

//Construct empty List
List::List()
{
first = NULL;

mySize = 0;
}

//Construct copy of source List
List::List( const List &source )
{
first = NULL;

mySize = -1;

int index = 0;

NodePointer current = source.first;

   while(current != NULL)
   {
       insert(current->data, index++);
       current = current->next;
   }
}

List::~List( )
{
for(int i = 0; i <= mySize; i++)
erase(i);
}

const List & List::operator=( const List &rightSide )
{
int index = 0;

NodePointer current = rightSide.first;

   while(current != NULL)
   {
       insert(current->data, index++);
       current = current->next;
   }

return *this;
}

int List::getSize( ) const
{
return mySize;
}

bool List::empty( ) const
{
if(mySize == -1)
return true;

return false;
}

void List::insert( ElementType dataVal, int index )
{

   if(index == 0)
   {
       NodePointer NewNode = new Node;

NewNode->data = dataVal;
NewNode->next = first;

first = NewNode;

       mySize++;
   }
   else if(index > 0 && index <= (mySize + 1))
   {
       NodePointer current = first;

for(int i = 0; i < index - 1; i++)
current = current->next;

NodePointer NewNode = new Node;

NewNode->data = dataVal;
NewNode->next = current->next;

current->next = NewNode;

mySize++;
}

}

void List::erase( int index )
{
   if(first != NULL)
   {
       if(index == 0)
       {
           NodePointer temp = first;

first = temp->next;

delete temp;

           mySize--;
       }
       else if(index > 0 && index <= (mySize + 1))
       {
           NodePointer current = first;

for(int i = 0; i < index -1; i++)
current = current->next;

NodePointer temp = current->next;

current->next = temp->next;

delete temp;

           mySize--;
       }
   }
}

void List::display( ostream &out ) const
{
NodePointer current = first;

   while(current != NULL)
   {
       out << current->data << endl;
       current = current->next;
   }
}

int List::find( ElementType value) const
{
NodePointer current = first;
int index = 0;

   while(current != NULL)
   {
       if(current->data == value)
           return index;
       else
       {
           current = current->next;
           index++;
       }
   }

return -1;
}
//----------------------------------------------------------------------------
// List.h

#ifndef LIST
#define LIST

#include <iostream>
#include <cstdlib>
#include <string>

using namespace std;

typedef string ElementType;

class List
{
private:

       class Node
       {
           public:

ElementType data;

Node * next;

Node( ): data( ElementType( ) ), next( NULL )
{ }

               Node( ElementType initData ): data( initData ), next( NULL )
               { }
       }; // end of Node class

typedef Node * NodePointer;

public:

List( );
/* Construct a List object

       Precondition: none.
       Postcondition: An empty List object has been constructed.
       */

List( const List &source );
/* Construct a copy of a List object.

       Precondition: None.
       Postcondition: A copy of source has been constructed.
       */

~List( );
/* Destroys a List object.

       Precondition: None.
       Postcondition: Any memory allocated to the List object has been freed.
       */

const List & operator=( const List &rightSide );
/* Assign a copy of a List object to the current object.

       Precondition: none
       Postcondition: A copy of rightside has been assigned to this
       object. A constant reference to this list is returned.
       */

int getSize( ) const;
/* Returns the size of the list (number of items in the list)

       Precondition: none
       Postcondition: The return value is the number of items in the list.
       */

bool empty( ) const;
/* Check if this List is empty

       Precondition: none
       Postcondition: The return value is true if this List object is empty;
       otherwise the return value is false.
       */

void insert( ElementType dataVal, int index );
/* Insert a value into this List at a given index

       Precondition: The index is valid (0 <= index <= the list size).
       The first position is index 0, the second position is index 1, etc.
       Postcondition: dataval has been inserted into the list at the position
       determined by index (provided there is room and index is a legal
       position).
       */

void erase( int index );
/* Remove the value from this List at a given index.

       Precondition: The list is not empty and index is valid
       (0 <= index < the list size).
       Postcondition: the element at position index has been
       removed (provided index is a legal position).
       */

void display( ostream &out ) const;
/* Display the contents of this List

       Precondition: ostream out is open
       Postcondition: the items in this List have been output to stream out
       */

int find( ElementType value) const;
/* Find the first occurrence of a value in this List

       Preconditions: None
       Postconditions: The return value is the index of the first List item
       that matches value. The first list item has index 0, the second has
       index 1, etc. The return value is -1 if value is not found in the list.
       */

private:

       NodePointer first;

       int mySize;

}; // end of List class

#endif

Explanation / Answer

// List.h

#ifndef LIST

#define LIST

#include <iostream>

#include <cstdlib>

#include <string>

using namespace std;

typedef string ElementType;

class List

{

private:

class Node

{

public:

ElementType data;

Node * next;

Node( ): data( ElementType( ) ), next( NULL )

{ }

Node( ElementType initData ): data( initData ), next( NULL )

{ }

}; // end of Node class

typedef Node * NodePointer;

public:

List( );

/* Construct a List object

Precondition: none.

Postcondition: An empty List object has been constructed.

List( const List &source );

/* Construct a copy of a List object.

Precondition: None.

Postcondition: A copy of source has been constructed.

~List( );

/* Destroys a List object.

Precondition: None.

Postcondition: Any memory allocated to the List object has been freed.

const List & operator=( const List &rightSide );

/* Assign a copy of a List object to the current object.

Precondition: none

Postcondition: A copy of rightside has been assigned to this

object. A constant reference to this list is returned.

int getSize( ) const;

/* Returns the size of the list (number of items in the list)

Precondition: none

Postcondition: The return value is the number of items in the list.

bool empty( ) const;

/* Check if this List is empty

Precondition: none

Postcondition: The return value is true if this List object is empty;

otherwise the return value is false.

void insert( ElementType dataVal, int index );

/* Insert a value into this List at a given index

Precondition: The index is valid (0 <= index <= the list size).

The first position is index 0, the second position is index 1, etc.

Postcondition: dataval has been inserted into the list at the position

determined by index (provided there is room and index is a legal

position).

void erase( int index );

/* Remove the value from this List at a given index.

Precondition: The list is not empty and index is valid

(0 <= index < the list size).

Postcondition: the element at position index has been

removed (provided index is a legal position).

void display( ostream &out ) const;

/* Display the contents of this List

Precondition: ostream out is open

Postcondition: the items in this List have been output to stream out

int find( ElementType value) const;

/* Find the first occurrence of a value in this List

Preconditions: None

Postconditions: The return value is the index of the first List item

that matches value. The first list item has index 0, the second has

index 1, etc. The return value is -1 if value is not found in the list.

private:

NodePointer first;

int mySize;

}; // end of List class

#endif

//List.cpp

#include "stdafx.h"

#include "List.h"

//Construct empty List

List::List()

{

first = NULL;

mySize = 0;

}

//Construct copy of source List

List::List( const List &source )

{

first = NULL;

mySize = 0; //check the code, the value of mySize is

//changed

int index = 0;

NodePointer current = source.first;

while(current != NULL)

{

insert(current->data, index++);

current = current->next;

}

List::~List( )

{

for(int i = 0; i <= mySize; i++)

erase(i);

}

const List & List::operator=( const List &rightSide )

{

int index = 0;

NodePointer current = rightSide.first;

while(current != NULL)

{

insert(current->data, index++);

current = current->next;

}

return *this;

}

int List::getSize( ) const

{

return mySize;

}

bool List::empty( ) const

{

if(mySize == -1)

return true;

return false;

}

void List::insert( ElementType dataVal, int index )

{

if(index == 0)

{

NodePointer NewNode = new Node;

NewNode->data = dataVal;

NewNode->next = first;

first = NewNode;

mySize++;

}

else if(index > 0 && index <= (mySize + 1))

{

NodePointer current = first;

for(int i = 0; i < index - 1; i++)

current = current->next;

NodePointer NewNode = new Node;

NewNode->data = dataVal;

NewNode->next = current->next;

current->next = NewNode;

mySize++;

}

void List::erase( int index )

{

if(first != NULL)

{

if(index == 0)

{

NodePointer temp = first;

first = temp->next;

delete temp;

mySize--;

}

else if(index > 0 && index <= (mySize + 1))

{

NodePointer current = first;

for(int i = 0; i < index -1; i++)

current = current->next;

NodePointer temp = current->next;

if(temp!=NULL) //check the condition that has been modified

current->next = temp->next;

delete temp;

mySize--;

}

void List::display( ostream &out ) const

{

NodePointer current = first;

while(current != NULL)

{

out << current->data << endl;

current = current->next;

}

int List::find( ElementType value) const

{

NodePointer current = first;

int index = 0;

while(current != NULL)

{

if(current->data == value)

return index;

else

{

index++;

current = current->next;

}

return -1;

}

// ListDemo.cpp : Defines the entry point for the console application.

#include "stdafx.h"

#include "List.h"

#include <iostream>

using namespace std;

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

{

List Test;

Test.insert("AAA", 0);

Test.insert("BBB", 1);

Test.insert("CCC", 2);

cout<<"The first list is: "<<endl;

Test.display(cout);

cout << Test.getSize() << endl;

List Test_Second;

Test_Second = Test;

cout<<"The Second list is: "<<endl;

Test_Second.display(cout);

cout << Test_Second.getSize() << endl;

Test_Second.insert("DDD", 3);

List Test_Third(Test_Second);

cout<<"The Third list is: "<<endl;

Test_Third.display(cout);

cout<<" " << Test_Third.getSize() << endl;

Test_Third.insert("EEE",4);

cout<<"The Third list after inserting another element is: "<<endl;

Test_Third.display(cout);

cout << Test_Third.getSize() << endl;

cout<<"Deleted an element whose index value is 2: "<<endl;

Test_Third.erase(2);

cout<<endl;

cout<<"Therefore, the elements present in the Third list are: "<<endl;

Test_Third.display(cout);

cout<<" "<<"The value AAA is found at: "<<Test_Third.find("AAA");

cout<<endl;

cout <<"The size of the Third list is :" <<Test_Third.getSize() << endl;

system ("pause");

return 0;

}

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

Sample Output:

The first list is:

AAA

BBB

CCC

The Second list is:

AAA

BBB

CCC

The Third list is:

AAA

BBB

CCC

DDD

The Third list after inserting another element is:

AAA

BBB

CCC

DDD

EEE

Deleted an element whose index value is 2:

Therefore, the elements present in the Third list are:

AAA

BBB

DDD

EEE

The value AAA is found at: 0

The size of the Third list is :4

Press any key to continue . . .

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

Note:

The code has been checked thoroughly, the change made are highligted in the bold letters. In the main function, to know which

list is getting displayed purpose, certain code has been added.

The changes made are:

1. in the parameterised constructor passing a reference to the List, the variable mysize is changed.

2. in the erase function, an if condition is added.

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