This C++ program implements a doubly linked list with the following functions: - create() adds a node to the empty list - append() adds a node to the end of the list - insert() inserts a node at a given index position - del() deletes a node with a given value - display() prints out the contents of the list It uses a node struct to define each list element and a DLL class to implement the linked list functions.

1. /*
* C++ Program to Implement Doubly Linked List
*/
#include
#include
#include
/*
* Node Declaration
*/
using namespace std;
struct node
{
int info;
struct node *next;
struct node *prev;
}*head;
/*
Class Declaration
*/
class dll
{
public:
void create(int value);
void append(int value);
void insert(int value, int index);
void del(int value);
void display();
dll()
{
head = NULL;
}
/* destructor*/
~dll()
{
node *ptr;

2. ptr = head;
while(ptr!=0){
node *next = ptr->next;
delete ptr;
ptr = next;
}
}
};
/*
* Main: Conatins Menu
*/
int main()
{
int option, element, index;
dll dl;
while (1)
{
cout<>option;
switch ( option )
{
case 1:
cout<<"Enter the element: ";
cin>>element;
dl.create(element);
cout<>element;
dl.append(element);
cout<>element;
cout<<"Insert Element after postion: ";
cin>>index;
dl.insert(element, index);
cout<>element;
dl.del(element);
cout<info = value;
temp->next = NULL;
if (head == NULL)
{

3. temp->prev = NULL;
head = temp;
}
else
{
s = head;
while (s->next != NULL)
s = s->next;
s->next = temp;
temp->prev = s;
}
}
/*
* Insertion at the beginning
*/
void dll::append(int value)
{
if (head == NULL)
{
cout<<"First Create the list."<prev = NULL;
temp->info = value;
temp->next = head;
head->prev = temp;
head = temp;
cout<<"Element Inserted"<next;
if (q == NULL)
{
cout<<"There are less than ";
cout<info = value;
if (q->next == NULL)
{
q->next = tmp;
tmp->next = NULL;
tmp->prev = q;
}
else

4. {
tmp->next = q->next;
tmp->next->prev = tmp;
q->next = tmp;
tmp->prev = q;
}
cout<<"Element Inserted"<info == value)
{
tmp = head;
head = head->next;
head->prev = NULL;
cout<<"Element Deleted"<next->next != NULL)
{
/*Element deleted in between*/
if (q->next->info == value)
{
tmp = q->next;
q->next = tmp->next;
tmp->next->prev = q;
cout<<"Element Deleted"<next;
}
/*last element deleted*/
if (q->next->info == value)
{
tmp = q->next;
free(tmp);
q->next = NULL;
cout<<"Element Deleted"<info<<" <-> ";
q = q->next;
}
cout<<"NULL"<
Solution
/*
* C++ Program to Implement Doubly Linked List
*/

5. #include
#include
#include
/*
* Node Declaration
*/
using namespace std;
struct node
{
int info;
struct node *next;
struct node *prev;
}*head;
/*
Class Declaration
*/
class dll
{
public:
void create(int value);
void append(int value);
void insert(int value, int index);
void del(int value);
void display();
dll()
{
head = NULL;
}
/* destructor*/
~dll()
{
node *ptr;
ptr = head;
while(ptr!=0){
node *next = ptr->next;
delete ptr;

6. ptr = next;
}
}
};
/*
* Main: Conatins Menu
*/
int main()
{
int option, element, index;
dll dl;
while (1)
{
cout<>option;
switch ( option )
{
case 1:
cout<<"Enter the element: ";
cin>>element;
dl.create(element);
cout<>element;
dl.append(element);
cout<>element;
cout<<"Insert Element after postion: ";
cin>>index;
dl.insert(element, index);
cout<>element;
dl.del(element);
cout<info = value;
temp->next = NULL;
if (head == NULL)
{
temp->prev = NULL;
head = temp;
}
else

7. {
s = head;
while (s->next != NULL)
s = s->next;
s->next = temp;
temp->prev = s;
}
}
/*
* Insertion at the beginning
*/
void dll::append(int value)
{
if (head == NULL)
{
cout<<"First Create the list."<prev = NULL;
temp->info = value;
temp->next = head;
head->prev = temp;
head = temp;
cout<<"Element Inserted"<next;
if (q == NULL)
{
cout<<"There are less than ";
cout<info = value;
if (q->next == NULL)
{
q->next = tmp;
tmp->next = NULL;
tmp->prev = q;
}
else
{
tmp->next = q->next;
tmp->next->prev = tmp;
q->next = tmp;

8. tmp->prev = q;
}
cout<<"Element Inserted"<info == value)
{
tmp = head;
head = head->next;
head->prev = NULL;
cout<<"Element Deleted"<next->next != NULL)
{
/*Element deleted in between*/
if (q->next->info == value)
{
tmp = q->next;
q->next = tmp->next;
tmp->next->prev = q;
cout<<"Element Deleted"<next;
}
/*last element deleted*/
if (q->next->info == value)
{
tmp = q->next;
free(tmp);
q->next = NULL;
cout<<"Element Deleted"<info<<" <-> ";
q = q->next;
}
cout<<"NULL"<