private void correctMaxUp(@Nullable IntervalNode<T> node) {
    int delta = node == null ? 0 : node.computeDeltaUpToRoot();
    assert delta == 0 : delta;
    while (node != null) {
      if (node.isValid()) {
        int d = node.delta;
        correctMax(node, delta);
        delta -= d;
      }
      node = node.getParent();
    }
    assert delta == 0 : delta;
  }
private void correctMaxUp(@Nullable IntervalNode<T> node)