Doubly link list

#include<bits/stdc++.h>
using namespace std;
class Node{
public:
    int data;
    Node *next;
    Node *prev;
};

class LinkList{
public:
    Node *head;
    LinkList(){
        head = NULL;
    }
    void insert_at_first( int value)
    {
        Node *newNode = new Node();
        newNode->data = value;
        newNode->next = head;
        newNode->prev = NULL;

        if( head != NULL)
        {
            head->prev = newNode;
        }
        head = newNode;
        //cout<<head->data;
    }
    ///insert after a specific node;
    void insert_at_middle(int value)
    {
        Node *temp = head->next;
        if( temp == NULL)
        {
            cout<<"The given previous node can not be NUlL";
            return ;
        }

        Node *newNode = new Node();
        newNode->data = value;
        newNode->next = temp->next;
        temp->next = newNode;

        newNode->prev = temp;

        if(newNode->next != NULL)
            newNode->next->prev = newNode;
    }
    void insert_after_value(int value,int key)
    {
        Node *temp = head;
        if(temp == NULL)
        {
            cout<<"Link list is empty";
            return ;
        }
        do{
            if(temp->data == key)
            {
                Node *newNode = new Node();
                newNode->data = value;
                newNode->next = temp->next;
                temp->next = newNode;
                newNode->prev = temp;
                if(newNode->next != NULL)
                {
                    newNode->next->prev = newNode;

                }
                return ;
            }
            temp = temp ->next;
        }while(temp != NULL);
        cout<<"Value is not found";
    }

    void insert_at_end( int value)
    {

        Node *temp = head;

        Node *newNode = new Node();
        newNode->data = value;
        newNode->next = NULL;

        if(head == NULL)
        {
            newNode->prev = NULL;
            head  = newNode;
            return ;
        }
        while( temp->next != NULL)
        {
            temp = temp->next;
        }
        temp->next = newNode;
        newNode->prev = temp;
    }


    void bubble_sort()
    {
        int swapped;
        Node *right_ptr = NULL;

        if( head == NULL)
            return ;
        do{
            swapped = 0;
            Node *temp = head;
            while ( temp->next != right_ptr)
            {
                if(temp->data > temp->next->data )
                {
                    swap(temp->data, temp->next->data);
                    swapped = 1;
                }
                temp = temp->next;
            }
            right_ptr = temp;
            //cout<<lptr<<endl;
        }while(swapped);
    }

    void delete_node(int key)
    {
        Node *temp = head,*previous;
        //cout<<temp->data;
        if( temp->data == key)
        {
            head = temp->next;
            head->prev = NULL;
            delete(temp);
            return;
        }
        while(temp != NULL && temp->data != key)
        {
            previous = temp;
            temp = temp->next;
        }
        if(temp == NULL)
        {
            cout<<"Value is not found";
            return;
        }
        cout<<previous->data;
        previous->next = temp->next;
        if(temp->next != NULL)
            previous->next->prev = previous;
    }

    void display()
    {
        Node *temp,*last;
        temp = head;
        cout<<"Traversal in forward direction "<<endl;
        while( temp != NULL)
        {
            cout<<temp->data<<" ";
            last = temp;
            temp = temp-> next;
        }

        cout<<endl<<" Traversal in reverse direction "<<endl;
        while(last != NULL)
        {
            cout<<last->data<<" ";
            last= last->prev;
        }
    }
    void reverse_List()
    {
        Node *temp = NULL;
        Node *curr = head;
        cout<<endl<<endl;
        while( curr != NULL)
        {
            ///swap between node previous and node next;
            temp = curr->prev;
            curr->prev = curr->next;
            curr->next = temp;
            curr = curr->prev;
        }

        if( temp != NULL)
            head = temp->prev;
    }

};
int main()
{
    LinkList ll;
    ll.insert_at_first(10);
    ll.insert_at_first(20);
    ll.insert_at_first(30);
    ll.insert_at_middle(500);
    ll.insert_at_end(600);
    ll.display();
    cout<<endl<<"which value after you want to insert"<<endl;
    int value;
    cin>>value;
    ll.insert_after_value(40,value);
    ll.display();

    cout<<endl<<"after reverse"<<endl;
    ll.reverse_List();
    ll.display();

    cout<<endl<<"After short"<<endl;

    ll.bubble_sort();
    ll.display();

    cout<<endl<<"After Delete"<<endl;
    cout<<"which value you want to delete"<<endl;
    cin>>value;
    ll.delete_node(value);
    ll.display();
}