/*
Name: S.R.Janhar 
Description: Doubly Linked List Program-Program to create a doubly linked list,to add an item(in front,in middle or in end),to delete an element(in front,in middle or in end) and to display to elements in the nodes. 
*/


#include<iostream.h> 
#include<conio.h> 
#include<stdlib.h> 
class dlink 
{ 
struct link 
{ 
int data; 
link *prev; 
link *next; 
}*head,*trav,*tptr; 
int p,flag,a,p1,b; 
public: 

void creation(int); 
void additem(int); 
void deletion(); 
void display(); 
dlink() 
{ 
head=NULL; 
} 
}; 

void dlink::creation(int i) 
{ 
link *newlink=new(link); 
if(head==NULL) 
{ 
newlink->data=i; 
newlink->prev=NULL; 
newlink->next=NULL; 
head=newlink; 
} 
else 
{ 
trav=head; 
while(trav->next!=NULL) 
{ 
trav=trav->next; 
} 
newlink->prev=trav; 
trav->next=newlink; 

newlink->data=i; 
newlink->next=NULL; 
} 
} 

void dlink::additem(int i) 
{ 
if(head==NULL) 
cout<<"\n DOUBLEY LINKED LIST NOT CREATED"; 
else 
{ 
cout<<" 1.Front, 2.Middle, 3.End \n"; 
cout<<" Your option : "; 
cin>>p; 
link *newlink=new(link); 
switch(p) 
{ 
case 1: 
newlink->data=i; 
newlink->next=head; 
head->prev=newlink; 
newlink->prev=NULL; 
head=newlink; 
break; 
case 2: 
cout<<"\nEnter the no. after which to be added : "; 
cin>>a; 
trav=head; 
tptr=head; 
while(trav->data!=a) 
{ 
tptr=trav->next->next; 
trav=trav->next; 
} 
newlink =new(link); 
newlink->prev=trav; 
newlink->next=tptr; 
newlink->data=i; 
tptr->prev=newlink; 
trav->next=newlink; 
break; 

case 3: 
trav=head; 
while(trav->next!=NULL) 
{ 
trav=trav->next; 
} 
trav->next=newlink; 
newlink->prev=trav; 
newlink->data=i; 
newlink->next=NULL; 
break; 
} 
} 
} 
void dlink::deletion() 
{ 
if(head==NULL) 
cout<<"\n DOUBLEY LINKED LIST NOT CREATED "; 
else 
{ 
cout<<" 1. Deletion in front, 2. Middle, 3.End \n"; 
cout<<"option : "; 
cin>>p1; 
switch(p1) 
{ 
case 1: 
if(head!=NULL) 
{ 
trav=head; 
trav=trav->next; 
trav->prev=NULL; 
head=trav; 
} 
else 
cout<<"\n doubley linked list not created "; 
break; 
case 2: 
if(head!=NULL) 
{ 
cout<<"enter the element to be deleted : "; 
cin>>b; 
trav=head; 
while(trav->data!=b) 
{ 
tptr=trav; 
trav=trav->next; 
} 
tptr->next=trav->next; 
trav->next->prev=tptr; 
} 
else 
cout<<"\n doubley linked list not created "; 
break; 
case 3: 
trav=head; 
while(trav->next!=NULL) 
{ 
tptr=trav; 
trav=trav->next; 
} 
tptr->next=NULL; 
trav=tptr; 
break; 
} 
} 
} 


void dlink::display() 
{ 
if(head==NULL) 
cout<<"\n NO ELEMENTS IN THE DOUBLEY LINKED LIST "; 
else 
{ 
cout<<" \n\n\t ELEMENTS IN THE DOUBLEY LINKED LIST ARE GIVEN BELOW : \n\n\n\n\t "; 
trav=head; 
while(trav->next!=NULL) 
{ 
cout<<trav->data<<" <==> "; 
trav=trav->next; 
} 
cout<<trav->data<<" <==> NULL"; 
} 
} 

void main() 
{ 
dlink d; 
int ch,x,y; 
do 
{ 
clrscr(); 
cout<<" \n\n\t\t PROGRAM FOR DOUBLEY LINKED LIST "; 
cout<<"\n\n\t Menu \n\n"; 
cout<<"\n\t\t 1. Creation "; 
cout<<"\n\t\t 2. Adding an element "; 
cout<<"\n\t\t 3. Deleting an element "; 
cout<<"\n\t\t 4. Display"; 
cout<<"\n\t\t 5. Exit \t"; 
cout<<"Opion : "; 
cin>>ch; 
switch(ch) 
{ 
case 1: 
do 
{ 

cout<<"\nEnter a +ve no. enter -ve no. to stop the creation : "; 
cin>>x; 
if(x>0) 
d.creation(x); 
} 
while(x>0); 
break; 

case 2: 
cout<<"\n\nEnter the element : "; 
cin>>y; 
d.additem(y); 
getch(); 
break; 

case 3: 
d.deletion(); 
getch(); 
break; 
case 4: 
d.display(); 
getch(); 
break; 
case 5: 
exit(0); 
break; 
default: 
cout<<"\n Enter the option between 1 and 5 :"; 
break; 
} 
} 
while(ch!=5); 
}