Delete middle node, 1st node or last node

Delete middle node, 1st node or last node

//deleting a particular node
#include<stdio.h>
#include<iostream.h>
#include<conio.h>
template<class T>
class node
{
 node<T> *llink;
 T data;
 node<T> *rlink;
 friend class dll<T>;
};
template <class T>
class dll
{
 private:
        node<T> *l,*r;
 public:
        dll();
       ~dll();
        int isempty();
        void display();
        int length();

        int del(int i);

void append(node<T>*k);
void create();
};
template<class T>
dll<T>::dll()
{
 l=r=NULL;
}
template<class T>
int dll<T>::isempty()
{
 return(l==NULL);
}
template<class T>
void dll<T>::display()
{

 node<T> *p;
 if(isempty())
 {
  cout<<"DLL is empty\n";
 }
 else
 {
   cout<<"DLL is as follows\n";
   for(p=l;p!=NULL;p=p->rlink)
     cout<<p->llink<<"\t"<<p->data<<"\t"<<p->rlink<<"\n";
 }
}
//length()
template<class T>
int dll<T>::length()
{
 int ctr=0;
 node<T> *p;
 p=l;
 while(p!=NULL)
 {
  ctr++;
  p=p->rlink;
 }
 return(ctr);
}
//apend()
template<class T>
void dll<T>::append(node<T>* k)
{
 node<T> *last;
 k->rlink=NULL;
 if(isempty())
   l=r=k;
 else
 {
   //last=r;
   last=l;
   while(last->rlink!=NULL)
   {
    last=last->rlink;
   }
   last->rlink=k;
   r=last;
  }
}
//create()
template<class T>
void dll<T>::create()
{
  T x;
  node<T> *k;
  l=r=NULL;
  cout<<"enter values terminated by -1 or !\n";
  cin>>x;
  while(x!=-1&&x!='!')
  {
   k=new node<T>;
   k->data=x;
   append(k);
   cin>>x;
   r=r->rlink;
  }
 }//create()

template<class T>
dll<T>::~dll()
{

}
//dele()
template <class T>
T dll<T>::del(int i)
{
 node<T>*p,*prev,*next;
 T x;
 if(i<1||i>length())
  return(-1);
 else if(l==r)
 {
  p=l;
  l=r=NULL;
  x=p->data;
  delete p;
  return(x);
 }
 else if(i==1)
 {
  p=l;
  l=l->rlink;
  l->llink=NULL;
  x=p->data;
  delete p;
  return(x);
 }
 else if(i==length())
 {
  p=r;
  r=r->llink;
  r->rlink=NULL;
  x=p->data;
  delete p;
  return(x);
 }
 else
 {
  p=l;
  for(int j=1;j<=i-1;j++)
   p=p->rlink;
  prev=p->llink;
  next=p->rlink;
  prev->rlink=next;
  next->llink=prev;
  x=p->data;
  delete p;
  return(x);
 }
}


main()
{
 dll<int>a;
 node<int>*p;
 int ch,i,x;
 clrscr();
 a.create();
 cout<<"enter value of i\n";
 cin>>i;
 x=a.del(i);
 if(x==-1)
  cout<<"Non-existing node\n";
 else
  cout<<"data of deleted node is"<<x<<"\n";
 a.display();

getch();
return(0);

}//main()

 Doubly Linked List Operations

Types of Linked list

1.     Single Linked List

2.    Doubly Linked List

3.    Circular Linked List 

Programs on Doubly Linked List

Node class structures

Some terminology of Doubly Linked List programs