Function rotate_left

src/tree/binary/rb.rs:204–221

左旋操作变换为: X Y / \ / \ a Y => X c / \ / \ b c a b */

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

 */
fn rotate_left<K, V>(
    mut root: Option<NonNull<Node<K, V>>>,
    x: NonNull<Node<K, V>>,
) -> Option<NonNull<Node<K, V>>> {
    let mut x = NodeQuery::new(Some(x));
    let p = x.parent();
    let mut y = x.right();
    let a = x.left();
    let b = y.left();
    let c = y.right();
    x.replace(y.node);
    x.set_children(a.node, b.node);
    y.set_children(x.node, c.node);
    if p.is_none() {
        root = y.node;
    }
    root
}

/*
右旋操作变换为: