The exercises are here https://news.ycombinator.com/item?id=15022458 (that post was downvoted & flagged to death, so you might have to turn on showdead in your profile to see it)

In a different comment chain on the same submission (https://news.ycombinator.com/item?id=15024640), he challenged the commenters disagreeing with him to do these exercises in 24 hours. The tone was pretty abrasive, TBH, but I found the questions interesting enough that I tackled them in earnest.

I posted my solution attempts, so don't scroll down too far if you want to try them on your own ;)