#include <iostream>
#include <stdlib.h>

using namespace std;


class list
{
    int leng;
    public:
        class element
        {
            public:
                friend class list_iterator;
                int data;
                element *next;
                element *prev;
                element()
                {
                    next = 0;
                    prev = 0;
                }
        };
        element *begin, *end;
        list ()
        {
            leng = 0;
            begin = end = new element;
        }
        void AddElement (int znach)
        {
            element *el = new element;
            end->data=znach;
            end -> next = el;
            el -> prev = end;
            end = el;
            leng++;
        }

        int getlen()
        {
            return (leng);
        }



};

class list_iterator
{
    list *p;
    list::element *e;
    int t;
    public:
        friend class list;
        list_iterator (list &l): p(&l), e(p->begin){}
        int gotonext()
        {
            if (e->next != 0)
            {
                t=e->data;
                e=e->next;
                return t;
            } else return (e->data);
        }
        int gotoprev()
        {
            if (e->prev != 0)
            {

                e=e->prev;
                return e->data;

            }  else return e->data;
        }

        int gotoend()
        {
            e = p->end;
            return e->data;
        }
        int gotobegin()
        {
            e = p->begin;
            return e->data;
        }
        void ChZn(int zn)
        {
            e->data = zn;
            return;
        }
        int getlen_iter()
        {
            int leng=0;
            list::element *poisk;
            poisk = p->begin;
            while (poisk->next != 0)
            {    poisk = poisk->next; leng++;}
            return leng;
        }

};


int main()
{
    list l;
    list_iterator b_to_e(l);
    list_iterator e_to_b(l);
    int data, leng;
    cout<<"Let's add some elements to list (0 = quit):"<<endl;
    do {
        cin>>data;
        l.AddElement(data);
    } while (data != 0);
    leng = b_to_e.getlen_iter();
    cout <<"Length of list is "<<leng<<endl;
    cout <<"Let's print our list from begin to end:"<<endl;
    b_to_e.gotobegin();
    for (int i=0; i<leng; i++)
        cout<<b_to_e.gotonext()<<" ";
    cout<<endl;

    cout << "Let's print out list from end to begin:"<<endl;
    e_to_b.gotoend();
    for (int i=0; i<leng; i++)
        cout<<e_to_b.gotoprev()<<" ";
    cout<<endl;

    cout << "Len's rotate list and print it rotated"<<endl;
    e_to_b.gotoend();
    b_to_e.gotobegin();
    for (int i=0; i<leng/2; i++)
    {
        data = b_to_e.gotonext();
        b_to_e.gotoprev();
        b_to_e.ChZn(e_to_b.gotoprev());
        e_to_b.ChZn(data);
        b_to_e.gotonext();
    }
    b_to_e.gotobegin();
    for (int i=0; i<leng; i++)
        cout<<b_to_e.gotonext()<<" ";
    cout<<endl;
    system("pause");
    return 0;
}