I was reading anudeep2011's blog.

He mentioned 2-3 lines down below to solve QTREE4 using HLD. I didn't understand it, can some explain it to me, please?

Here is the link to the problem.

I read elsewhere, that it can be solved by Centroid Decomposition too, but I need to understand the HLD approach.

EDIT: Now I'm wondering if he wrote those 2-3 lines under QTREE4 by mistake. Because just below it, he says that QTREE5 is a "bit hard", and it is almost the same problem (maximum -> minimum).