/*
* Doubly linked list implementation in c++.
* operations:
* 1-> Insert at head.
* 2-> print forward.
* 3-> print reverse order.
*/
#include
using namespace std;
struct node
{
    int data;
    node* next;
    node* prev;
};
class d_list
{
private:
    node* head;
    node* GetNewNode(int n)
    {
        node* newNode = new node();
        newNode->data = n;
        newNode->next = NULL;
        newNode->prev = NULL;
        return newNode;
    }
public:
    d_list()
    {
        head = NULL;
    }
    void InsertAtHead(int n)
    {
        node* temp = GetNewNode(n);
        if (head == NULL)
        {
            head = temp;
            return;
        }
        head->prev = temp;
        temp->next = head;
        head = temp;
    }
    void print()
    {
        node* t = head;
        cout << "Forward: ";
        while (t!=NULL)
        {
            cout << t->data << " ";
            t = t->next;
        }
        cout << "\n";
    }
    void print_reverse()
    {
        node* t = head;
        while (t->next != NULL)
        {
            t = t->next;
        }
        //reverse
        cout << "reverse: ";
        while (t != NULL)
        {
            cout << t->data << " ";
            t = t->prev;
        }
        cout << "\n";
    }
};

int main()
{
    d_list l;     //object from class doubly list
    l.InsertAtHead(1);
    l.InsertAtHead(2);    //function insert at beginning
    l.InsertAtHead(3);
    l.print();             //List should print: 3 2 1
    l.print_reverse();     //List should print: 1 2 3
    return 0;
}