Question

Add a copy constructor for the linked list implementation below:

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

// list.cpp file

#include <string>
#include "list.h"

using namespace std;

Node::Node(string element)
{
data = element;
previous = nullptr;
next = nullptr;
}

List::List()
{
first = nullptr;
last = nullptr;
}

List::List(const List& rhs) // Copy constructor - homework
{
// Your code here
  
}

void List::push_back(string element)
{
Node* new_node = new Node(element);
if (last == nullptr) // List is empty
{
first = new_node;
last = new_node;
}
else
{
new_node->previous = last;
last->next = new_node;
last = new_node;
}
}

void List::insert(Iterator iter, string element)
{
if (iter.position == nullptr)
{
push_back(element);
return;
}

Node* after = iter.position;
Node* before = after->previous;
Node* new_node = new Node(element);
new_node->previous = before;
new_node->next = after;
after->previous = new_node;
if (before == nullptr) // Insert at beginning
{
first = new_node;
}
else
{
before->next = new_node;
}
}

Iterator List::erase(Iterator iter)
{
Node* remove = iter.position;
Node* before = remove->previous;
Node* after = remove->next;
if (remove == first)
{
first = after;
}
else
{
before->next = after;
}
if (remove == last)
{
last = before;
}
else
{
after->previous = before;
}
delete remove;
Iterator r;
r.position = after;
r.container = this;
return r;
}

Iterator List::begin()
{
Iterator iter;
iter.position = first;
iter.container = this;
return iter;
}

Iterator List::end()
{
Iterator iter;
iter.position = nullptr;
iter.container = this;
return iter;
}

Iterator::Iterator()
{
position = nullptr;
container = nullptr;
}

string Iterator::get() const
{
return position->data;
}

void Iterator::next()
{
position = position->next;
}

void Iterator::previous()
{
if (position == nullptr)
{
position = container->last;
}
else
{
position = position->previous;
}
}

bool Iterator::equals(Iterator other) const
{
return position == other.position;
}

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

Use the following header file, and test program (not to be modified) to verify that the copy constructor works correctly:

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

// list.h file

#ifndef LIST_H
#define LIST_H

#include <string>

using namespace std;

class List;
class Iterator;
//template <typename T>
class Node
{
public:
/**
Constructs a node with a given data value.
@param element the data to store in this node
*/
Node(string element); // Node(T element)
// Node(T data, Node<T>* n, Node<T>* n);
private:
string data; // T data;
Node* previous;
Node* next;
friend class List;
friend class Iterator;
};

class List
{
public:
/**
Constructs an empty list.
*/
List();
List(const List& rhs); // Homework
/*
Appends an element to the list.
@param element the value to append
*/
void push_back(string element);
/**
Inserts an element into the list.
@param iter the position before which to insert
@param element the value to insert
*/
void insert(Iterator iter, string element);
/**
Removes an element from the list.
@param iter the position to remove
@return an iterator pointing to the element after the
erased element
*/
Iterator erase(Iterator iter);
/**
Gets the beginning position of the list.
@return an iterator pointing to the beginning of the list
*/
Iterator begin();
/**
Gets the past-the-end position of the list.
@return an iterator pointing past the end of the list
*/
Iterator end();
private:
Node* first;
Node* last;
friend class Iterator;
};

class Iterator
{
public:
/**
Constructs an iterator that does not point into any list.
*/
Iterator();
/**
Looks up the value at a position.
@return the value of the node to which the iterator points
*/
string get() const;
/**
Advances the iterator to the next node.
*/
void next();
/**
Moves the iterator to the previous node.
*/
void previous();
/**
Compares two iterators.
@param other the iterator to compare with this iterator
@return true if this iterator and other are equal
*/
bool equals(Iterator other) const;
private:
Node* position;
List* container;
friend class List;
};

#endif

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

// list_test .cpp file

#include <string>
#include <iostream>
#include "list.h"

using namespace std;

int main()
{
List names;

names.push_back("Tom");
names.push_back("Diana");
names.push_back("Harry");
names.push_back("Juliet");

// Add a value in fourth place

Iterator pos = names.begin();
pos.next();
pos.next();
pos.next();

names.insert(pos, "Romeo");

// Remove the value in second place

pos = names.begin();
pos.next();

names.erase(pos);

List names_copy(names); //Copy constructor - homework
names_copy.push_back("Shakespeare");
// Verify that Shakespeare was inserted.
cout << "Printing new list" << endl;
for (pos = names_copy.begin(); !pos.equals(names.end()); pos.next())
{
cout << pos.get() << endl; //
}
cout << "Printing original list " << endl;
for (pos = names.begin(); !pos.equals(names.end()); pos.next())
{
cout << pos.get() << endl;
}

return 0;
}

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

Thank you for your time and help!

Answer 1

/* list.h */

#ifndef LIST_H
#define LIST_H

#include <string>

using namespace std;

class List;
class Iterator;
//template <typename T>
class Node
{
public:
/**
Constructs a node with a given data value.
@param element the data to store in this node
*/
Node(string element); // Node(T element)
// Node(T data, Node<T>* n, Node<T>* n);
private:
string data; // T data;
Node* previous;
Node* next;
friend class List;
friend class Iterator;
};

class List
{
public:
/**
Constructs an empty list.
*/
List();
List(const List& rhs); // Homework
/*
Appends an element to the list.
@param element the value to append
*/
void push_back(string element);
/**
Inserts an element into the list.
@param iter the position before which to insert
@param element the value to insert
*/
void insert(Iterator iter, string element);
/**
Removes an element from the list.
@param iter the position to remove
@return an iterator pointing to the element after the
erased element
*/
Iterator erase(Iterator iter);
/**
Gets the beginning position of the list.
@return an iterator pointing to the beginning of the list
*/
Iterator begin();
/**
Gets the past-the-end position of the list.
@return an iterator pointing past the end of the list
*/
Iterator end();
private:
Node* first;
Node* last;
friend class Iterator;
};

class Iterator
{
public:
/**
Constructs an iterator that does not point into any list.
*/
Iterator();
/**
Looks up the value at a position.
@return the value of the node to which the iterator points
*/
string get() const;
/**
Advances the iterator to the next node.
*/
void next();
/**
Moves the iterator to the previous node.
*/
void previous();
/**
Compares two iterators.
@param other the iterator to compare with this iterator
@return true if this iterator and other are equal
*/
bool equals(Iterator other) const;
private:
Node* position;
List* container;
friend class List;
};

#endif

/* list.cpp */

#include <string>
#include "list.h"

using namespace std;

Node::Node(string element)
{
data = element;
previous = nullptr;
next = nullptr;
}

List::List()
{
first = nullptr;
last = nullptr;
}

List::List(const List& rhs) // Copy constructor - homework
{
   Node *p = rhs.first;
first = last = NULL;
while(p!=NULL){
this->push_back(p->data);
p=p->next;
}
  
}

void List::push_back(string element)
{
Node* new_node = new Node(element);
if (last == nullptr) // List is empty
{
first = new_node;
last = new_node;
}
else
{
new_node->previous = last;
last->next = new_node;
last = new_node;
}
}

void List::insert(Iterator iter, string element)
{
if (iter.position == nullptr)
{
push_back(element);
return;
}

Node* after = iter.position;
Node* before = after->previous;
Node* new_node = new Node(element);
new_node->previous = before;
new_node->next = after;
after->previous = new_node;
if (before == nullptr) // Insert at beginning
{
first = new_node;
}
else
{
before->next = new_node;
}
}

Iterator List::erase(Iterator iter)
{
Node* remove = iter.position;
Node* before = remove->previous;
Node* after = remove->next;
if (remove == first)
{
first = after;
}
else
{
before->next = after;
}
if (remove == last)
{
last = before;
}
else
{
after->previous = before;
}
delete remove;
Iterator r;
r.position = after;
r.container = this;
return r;
}

Iterator List::begin()
{
Iterator iter;
iter.position = first;
iter.container = this;
return iter;
}

Iterator List::end()
{
Iterator iter;
iter.position = nullptr;
iter.container = this;
return iter;
}

Iterator::Iterator()
{
position = nullptr;
container = nullptr;
}

string Iterator::get() const
{
return position->data;
}

void Iterator::next()
{
position = position->next;
}

void Iterator::previous()
{
if (position == nullptr)
{
position = container->last;
}
else
{
position = position->previous;
}
}

bool Iterator::equals(Iterator other) const
{
return position == other.position;
}

/* list_test.cpp*/

#include <string>
#include <iostream>
#include "list.cpp"

using namespace std;

int main()
{
List names;

names.push_back("Tom");
names.push_back("Diana");
names.push_back("Harry");
names.push_back("Juliet");

// Add a value in fourth place

Iterator pos = names.begin();
pos.next();
pos.next();
pos.next();

names.insert(pos, "Romeo");

// Remove the value in second place

pos = names.begin();
pos.next();

names.erase(pos);

List names_copy(names); //Copy constructor - homework
names_copy.push_back("Shakespeare");
// Verify that Shakespeare was inserted.
cout << "Printing new list" << endl;
for (pos = names_copy.begin(); !pos.equals(names.end()); pos.next())
{
cout << pos.get() << endl; //
}
cout << "Printing original list " << endl;
for (pos = names.begin(); !pos.equals(names.end()); pos.next())
{
cout << pos.get() << endl;
}

return 0;
}

/* OUTPUT */

/* PLEASE UPVOTE */