Method right_subtree

publication/code/chapter08/avl.rs:188–193

(&mut self)

    }

    fn right_subtree(&mut self) -> &mut Self {
        match self {
            Null => panic!("Error: Empty tree!"),
            Tree(node) => &mut node.right,
        }
    }

    // 左右旋
    fn rotate_left(&mut self) {