This is my personal note and might be some kind of user editorial/learning material for some people!
This is the fourth episode of this "note" series. I will write notes on problems (normally around 2400-ish problems), which are solved without looking at the editorial, that are both interesting and educational. I normally will spend a few hours on each problem so please be patient when reading the blog.
If you want to motivate me to write a continuation (aka note 5), a significant upvote from you would be well appreciated! If I received lots of downvotes (because I'm also spending a lot of time to write this and to learn latex only to express my ideas accurately to you guys), I'm probably not gonna continuing writing these blogs.
Problem statement:
Given a tree with $$$N$$$ nodes. You are given $$$Q$$$ queries. For each query, you are given an integer $$$K$$$ and an array $$${a}$$$ of length $$$K$$$.
We will color all these nodes in $$${a}$$$ in red.
$$$\sum_{i=1}^{Q}K_{i} \leq 10^5, 1 \leq N,Q\leq 10^5$$$.
Enemies will try to disconnect these nodes by removing other nodes that are not in $$${a}$$$. Find minimum nodes (that are not in $$${a}$$$) removed in order to disconnect those nodes in $$${a}$$$. Queries are not permanent (the nodes destroyed will be resetted after the query).
Are you able to find the full solution from the hints?