Function calc_blacks

src/tree/binary/rb2.rs:416–426

(x: Option<NonNull<Node<K, V>>>)

}

fn calc_blacks<K, V>(x: Option<NonNull<Node<K, V>>>) -> usize {
    let mut x = NodeQuery::new(x);
    let mut black = 0;
    while x.is_some() {
        if !x.is_red() {
            black += 1;
        }
        x = x.left();
    }
    black
}

#[test]
fn t_verify() {