YouTube's community post system is kinda bad, so I'll make an explicit blog about this so people here can see it too. You can probably see on the sidebar that there will be another topic stream tomorrowish, and it'll be about general tree problems. Like last time, I've prepared a mashup, which can be found here: https://codeforces.com/contestInvitation/06ef32f75d130163cc2536475b38aebe91ba3113. There are 8 problems, essentially hand-picked this time to either be cool problems or include some topic I wanted to cover. A warning: the last problem is much harder than the others.
Making a blog for each of these (there will probably be many in the future) seems kinda annoying though. Maybe a good solution would be to add some sort of "description" field to streams on Codeforces, since that doesn't exist on Twitch (except for channel description), and most people probably wouldn't look at the YouTube description?
I'll give an intro to trees, but it may also be a good idea to be familiar with them beforehand. For example, one useful thing for this would be the well-known tree basics video (by our lord and savior SecondThread).