bool check(const BinTree* b) {
    if (empty(b)) return true;
    int r = 0, rl = 0, rr = 0;
    r = root(b);
    if (right(b) && left(b)){
        rl = root(left(b));
        rr = root(right(b));
        if(rl == 2*r && rr == 2*r+1)
            return (check(left(b))&&check(right(b)));
        else return false;
    }
    else if(left(b)) {
        rl = root(left(b));
        if(rl == r * 2) return check(left(b));
        else return false;
    }
    else if(right(b)) {
        rl = root(right(b));
        if(rl == r * 2+1) return check(right(b));
        else return false;
    }
    else return true;
    return true;
}