#include<iostream>

using namespace::std;

 class item{

  public:

   int key;

    float data;

    item* next;

    item* prev;

    item(int k,float d){

     key=k;

     data=d;

     next=NULL;

     prev=NULL;

    }

 void display(){

  cout<<"Key Is : "<<key<<" & Data Is : "<<data<<endl;

 }

 };

 class linkedList{

  private:

   item* tail;

   item* head;

   public:

    linkedList(){

     head=NULL;

     tail=NULL;

    }

    void insertAtTail(item* i)

    {

      if(head==NULL)

      {

           head=i;

        tail=i;

      }

    else{

       item* curr=head;

       while(curr->next!=NULL)

       {

          curr=curr->next;

       }

     curr->next=i;

     i->prev=curr;

     tail=tail->next;

    }

    }

   void insertAtHead(item* i)

   { 

     if(head==NULL)

     {

          head=i;

     }else{

         i->next=head;

         head->prev=i;

         head=i;

     }

   }

  void displayList()

  {

       if(head==NULL)

       cout<<"List Is Empty ! "<<endl;

       else{

            item* curr=head;

            cout<<"\t\t*** => Displaying List : "<<endl<<endl;

            while(curr!=NULL)

            {

                 curr->display();

                 curr=curr->next;

      }

    }

  }

 void delAtTail(){

    cout<<"\t\t\t***** After Del At Tail *****"<<endl<<endl;

    item* curr=tail;

    tail=tail->prev;

    tail->next=NULL;

    curr->prev=NULL;

    delete curr;

 }

void delAtHead(){

   cout<<"\t\t\t********** After Delete At Head **********"<<endl<<endl;

 item* curr=head;

 head=head->next;

 head->prev=NULL;

 delete curr;

}

   void displayFromHead(){

    if(head==tail)

    {

        cout<<"List is empty !"<<endl;

    }else{

           cout<<"\t\t\t**********  Displaying From Head To Tail **********"<<endl<<endl;

          item* curr=head;

          while(curr!=NULL)

          {

               curr->display();

               curr=curr->next;

    }

         }

   }

    void displayFromTail(){

     if(head==tail)

    {

        cout<<"List is empty !"<<endl;

    }else{

           cout<<"\t\t\t********** Displaying From Tail To Head **********"<<endl<<endl;

                    item* curr=tail;

     while(curr!=NULL)

     {

        curr->display();

        curr=curr->prev;

     }

    }

         } 

 };

 int main()

 {

     linkedList *list=new linkedList();

     list->insertAtTail(new item(3,4.5));

     list->insertAtTail(new item(1,2.3));

     list->insertAtTail(new item(4,5.6));

     list->insertAtTail(new item(2,3.4));

       list->displayList();

    list->delAtTail();

     list->displayList();

     list->delAtHead();

     list->displayList();

     list->displayFromHead();

       list->displayFromTail();

    list->displayList(); 

 }