Seeing tree problems with long problem statements and diagrams the first thought that comes to mind is "Oh no, here comes more work, but I have to tackle it for any hope of getting better at CP."

I'm currently working on this : https://mirror.codeforces.com/contest/1843/problem/D

Leave a comment on some of the best tree problems you've worked on. How easy/difficult it was to solve? What was the crux move/idea? ...