It was solved by just 80 people in Oct long challenge which is a very big thing for me. I just read the statement and went to sleep. In the middle of night I just woke up with the solution. I was suprised to see my solution got accepted so easily. It was an amazing experience for me as I hardly thought about its solution for more than a minute.
[1]: CodeChef: Practical coding for everyone
I will uptove ASTRD. And further throw in MGCHGEOM because I learned way too much while working on this and spent pretty much the entirety of 3 days on it. TULIPS was another one that took a long time but again taught me a lot.
I voted for the following 3 problems (for the following reasons):
CHNBGMT: I learnt a new lemma which was needed in order to solve this problem 100%.
CHEFPOL: It seemed hard when I first looked at it, but the code ended up being so short and easy to write.
BOUNCE: Hard number theory problem; even after having the right idea, I had to do lots of algorithmic and low-level optimizations to make my solution run in time (sadly there’s no editorial for it, yet).
PS: I already edited the question to assign votes to these problems.
@pkacprzak, as far as I remember only the author or someone with more than 1.5/2k karma points only can edit the wiki post and for others, even the “Edit” button is not available