Can someone show me how to complete the copy constructor, assignment operator, a
ID: 3673447 • Letter: C
Question
Can someone show me how to complete the copy constructor, assignment operator, and output operator in the following c++ header file?
#include <cstdlib>
#include <iostream>
using namespace std;
class DoublyLinkedList; // class declaration
// list node
class DListNode {
private: int obj;
DListNode *prev, *next;
friend class DoublyLinkedList;
public:
DListNode(int e=0, DListNode *p = NULL, DListNode *n = NULL)
: obj(e), prev(p), next(n) {}
int getElem() const { return obj; }
DListNode * getNext() const { return next; }
DListNode * getPrev() const { return prev; }
};
// doubly linked list
class DoublyLinkedList {
protected: DListNode header, trailer;
public:
DoublyLinkedList() : header(0), trailer(0) // constructor
{ header.next = &trailer; trailer.prev = &header; }
DoublyLinkedList(const DoublyLinkedList& dll); // copy constructor
~DoublyLinkedList(); // destructor
DoublyLinkedList& operator=(const DoublyLinkedList& dll); // assignment operator
// return the pointer to the first node
DListNode *getFirst() const { return header.next; }
// return the pointer to the trailer
const DListNode *getAfterLast() const { return &trailer; }
// return if the list is empty
bool isEmpty() const { return header.next == &trailer; }
int first() const; // return the first object
int last() const; // return the last object
void insertFirst(int newobj); // insert to the first of the list
int removeFirst(); // remove the first node
void insertLast(int newobj); // insert to the last of the list
int removeLast(); // remove the last node
};
// output operator
ostream& operator<<(ostream& out, const DoublyLinkedList& dll);
Explanation / Answer
Answer:
// copy constructor
template <class T> DoublyLinkedList<T>::DoublyLinkedList(DoublyLinkedList<T>& dll)
{
header.next = &trailer;
trailer.prev = &header;
if (!dll.isEmpty())
{
DListNode<T>* element;
element=dll.getFirst();
while (element!=dll.getAfterLast())
{
insertLast(element->getElem());
element=element->getNext();
}
}
}
// assignment operator
template <class T> DoublyLinkedList<T>& DoublyLinkedList<T>::operator=(DoublyLinkedList<T>& dll)
{
DListNode<T> *prev_node, *element = header.next;
while (element!= &trailer)
{
prev_node = element;
element = element->next;
delete prev_node;
}
header.next = &trailer;
trailer.prev = &header;
if (!dll.isEmpty())
{
element=dll.getFirst();
while (element!=dll.getAfterLast())
{
insertLast(element->getElem());
element=element->getNext();
}
}
}
// output operator
template <class T> ostream& operator<<(ostream& out, DoublyLinkedList<T>& dll)
{
DListNode<T>* read=dll.getFirst();
while (read!=dll.getAfterLast())
{ T object=read->getElem();
out<<object<<endl;
read=read->getNext();
}
return out;
}