• DSU → Disjoint Set Union / the Union–Find (or union–find) data structure; Why called "DSU":

https://notes.sshwy.name/DSU-on-tree/

https://oi-wiki.org//ds/dsu/#启发式合并

tutor: https://codeforces.com/blog/entry/44351

detailed explain: https://codeforces.com/blog/entry/67696