public String toStringIterativePostorder(BSTNode<T> t) {
		String salida = "";
		Stack <BSTNode<T>> pila = new ALStack<BSTNode<T>>();
		pila.push(null);
		Stack<Boolean> izquierdo = new ALStack <Boolean>();
		BSTNode<T> act = root;
		while (act != null) {
			while (act != null) {
				pila.push(act);
				izquierdo.push(true);
				if (act.right != null) {
					pila.push(act.right);
					izquierdo.push(false);
				}
				act = act.left;
			}
			act = pila.pop();
			while (act != null && izquierdo.pop()) {
				salida += act.nodeValue + "  ";
				act = pila.pop();
			}
		}
		return salida;
	}