COMPLEJIDAD PREORDEN

                                                                               //O(1)
     public Iterator<T> preOrden(){                                             //T=2+2+2 = 6
         ListaCD<T> l=new ListaCD<T>();                                         //2
         preOrden(this.getRaiz(),l);                                         //2
         return (l.iterator());                                                 //2
        }
T=2+2+2 = 6

T=6

O(1)