codice:
nodo *dealloca_k_nodi( nodo *P, int &k )
{
    while( P && k>0 )
    {
        nodo *t = P->next;
        delete P;
        P = dealloca_k_nodi( t, --k );
    }
    return P;
}


void stampa(nodo* P)
{
    if( P )
    {
        cout<< P->info << ' ';
        stampa(P->next);
    }
}