COMPLEJIDAD TOSTRING

                                                                       //O(n)
    public String toString(){                             //T=2+max(1,)+1+8+E(4+5)+1
        if (this.esVacia())                                                     //2
            return ("Lista Vacia");                                             //1
        String r="";                                                            //1
        for(NodoD<T> x=this.cabeza.getSig();x.getInfo()!=null;x=x.getSig())     //8+E(4)
            r+=x.getInfo().toString()+"<->";                                    //5
        return(r);                                                              //1
    }

T = 2+1+1+8+4n+5n+1 = 13+9n

O(n)