I was practising a question from Atcoder abc287 f, while reading the editorial for this problem, I encountered something called "square-order tree DP" due to it, by doing a process, which seems O(n^3) at first glance is actually O(n^2) they had linked a blog about it, but it is in Japanese, and I wasn't able to find a relevant resource related to it, in English, if someone, can help me find a relevant resource, or explain why the process is O(n^2) it would be very helpful.