public static boolean tuttiDiversiAlLivello(AlberoBin<Integer>a, int l){
        if (a==null)return false;
        AlberoBin<Integer> b = a;
        if (valoreTrovato(a.val(),l,0,b))
            return false;
        l++;
        if(a.sin()==null && a.des()== null)
            l=0;
        return tuttiDiversiAlLivello(a.sin(),l) && tuttiDiversiAlLivello(a.des(),l);
    }
    private static boolean valoreTrovato(Integer val, int livA, int livB, AlberoBin<Integer> b) {
        if(b==null)return false;
        if(livB !=0 && livA==livB && val == b.val())
            return true;
        livB++;
        if(b.sin()==null && b.des()==null)
            livB=0;
        return valoreTrovato(val,livA,livB,b.sin()) && valoreTrovato(val,livA,livB,b.des());
    }