#include <QtCore/QCoreApplication>
#include <iostream>

template <class Data> class List{
    class Node{
        public:
            Data d;
            Node *next, *prev;
            Node(Data dat = 0){d = dat; next = 0; prev = 0;}
    };

    Node *pbeg, *pend;
        public:
        List(){pbeg = 0; pend = 0;}
        ~List();
    void add(Data d);
    Node * find(Data i);
    Node * insert(Data key, Data d);
    bool remove(Data key);
    void print();
    void print_back();
};



//-------------------------------------
template <class Data>
List <Data>::~List(){
if (pbeg !=0){
Node *pv = pbeg;
while (pv){
pv = pv->next; delete pbeg;
pbeg = pv;}
    }
}

//-------------------------------------

template <class Data>
void List <Data>::print(){
Node *pv = pbeg;
std::cout << std::endl << "list: ";
while (pv){
std::cout << pv->d << ' ';
pv = pv->next;}
std::cout << std::endl;
}

//-------------------------------------

template <class Data>
void List <Data>::print_back(){
Node *pv = pend;
std::cout << std::endl << " list back: ";
while (pv){
std::cout << pv->d << ' ';
pv = pv->prev;}
std::cout << std::endl;
}

//-------------------------------------

template <class Data>
void List <Data>::add(Data d){
Node *pv = new Node(d);
if (pbeg == 0)pbeg = pend = pv;
else{
pv->prev = pend;
pend->next = pv;
pend = pv;}
}

//-------------------------------------

template <class Data>
Node * List <Data>::find(Data d){
Node *pv = pbeg;
while (pv){
if(pv->d == d)break;
pv = pv->next;
}
return pv;
}

//------------------------------------

template <class Data>
Node * List<Data>::insert(Data key, Data d){
if(Node *pkey = find(key)){
Node *pv = new Node(d);
pv->next = pkey->next;

pv->prev = pkey;
pkey->next =* pv;
if (pkey != pend)(pv->next)->prev = pv;
else pend = pv;
return pv;}
return 0;
}

template <class Data>
bool List <Data>::remove(Data key){
    if(Node *pkey = find(key)){
        if (pkey == pbeg){
        pbeg = pbeg->next; pbeg->prev = 0;}
        else if(pkey == pend){
        pend = pend->prev; pend->next = 0;}
    else {
         (pkey->prev)->next = pkey->next;
         (pkey->next)->prev = pkey->prev;}
         delete pkey; return true;}
         return false;
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    
    return a.exec();
}

typedef List<class Data> lst;

  lst lst1;
    for(int i = 0; i < 8; ++i) lst1::add(i);