COMPLEJIDAD POSTORDEN_ITERATIVO

                                                                                //O(n)
    private String postOrden_Iterativo(NodoBin<T> r){                           //T=2+2+1+2+E(2+8+max(2+2, 7+max(5+1+2+max(2,1),5+max(2+2,5+max(5+1+2+max(2,1),0)))))+1 = 8+n(10+7+5+5+10) = 8+37n
        Pila<NodoBin> pila = new Pila<NodoBin>();                               //2
        NodoBin<T> tope = null;                                                 //2
        String rr="";                                                           //1
        while(r!=null)                                                          //2+E(2)
        {   
            if(r.getIzq()!=null && r.getIzq()!=tope && r.getDer()!=tope){        //8+max
                pila.apilar(r);                                             //2
                r=r.getIzq();                                                   //2
            }
            else 
                if(r.getIzq()==null && r.getDer()==null && r!=tope){            //7+max
            
                rr+=r.getInfo().toString()+"-";                                 //5
                tope=r;                                                         //1
                if(!pila.esVacia())                                             // 2   +max  
                    r = pila.desapilar();                                       //2
                else r =null;                                                   // 1 
            }   
            else 
                if(r.getDer()!=null && tope!=r.getDer()){                       //5+max
                pila.apilar(r);                                             //2
                r=r.getDer();                                                   //2
            }   
            else 
                if(r.getDer()!=null && tope==r.getDer()){                       //5+max                                               
                rr+=r.getInfo().toString()+"-";                                 //5
                tope=r;                                                         //1
                if(!pila.esVacia())                                             //2+max
                    r = pila.desapilar();                                       //2
                else r =null;                                                   //1
            }
        }
        return (rr);                                                            //1
    }
T=2+2+1+2+\sum_{1=0}^{n}(2+8+max(2+2, 7+max(5+1+2+max(2,1),5+max(2+2,5+max(5+1+2+max(2,1),0)))))+1
T=8+n(10+7+5+5+10) = 8+37n

T=37n

O(n)