Method splay

Data Structures/Top Tree.cpp:262–274

  }

  void splay() {
    assert(!is_vert);
    while (!r()) {
      if (!p->r()) {
        if (p->d() == d()) {
          p->rot();
        } else {
          rot();
        }
      }
      rot();
    }
  }

  top_tree_node* cut_right() {
    assert(is_vert && is_path);