Method rotate_left

publication/code/chapter08/avl.rs:196–203

左右旋

(&mut self)

    // 左右旋
    fn rotate_left(&mut self) {
        let mut n = replace(self, Null);
        let mut right = replace(n.right_subtree(), Null);
        let right_left = replace(right.left_subtree(), Null);
        *n.right_subtree() = right_left;
        *right.left_subtree() = n;
        *self = right;
    }

    fn rotate_right(&mut self) {
        let mut n = replace(self, Null);