int Tree::size(Node* n) {
    int s = 0;
    if (n != NULL) {
        s += size(n->left());
        s += size(n->right());
        return ++s;
    }
    else
        return 0;
}

int Tree::height(Node* n) {
    int left = 0;
    int right = 0;
    if (!empty(n)) {
        left += height(n->left());
        right += height(n->right());

        left++;
        right++;
        if (left > right)
            return left;
        else
            return right;
    }
    else
        return 0;
}