From my side, I can only be sorry due to the fact that the problems were too similar, but as I’ve mentioned to some people, they were devised with some months time difference, and, as such, I was completely unaware that they could be used together on the same contest.
MCHAIRS was actually written not even thinking about the binary exponentiation method, as I had seen its original derivation formula as a modifcation of the Binomial Theorem, so, I really didn’t thought about it much.
SPOTWO was intended to be an easy problem and I wrote my solution being mostly concerned with the implementation of a long arithmetic idea to “avoid” overflow of the number
2*N_bin… (I knew that around the number 524 thousand and something or 527 thousand and something, the number
2*N_bin would exceed the value of an ULL and that was the only reason I used 600.000 as an upper limit - again - I didn’t even realized the problem could be so easily solved as almost everyone did).
On the other hand, if I had found some way of failing the most naive solutions and use only the idea that Hiroto told me about (which is largely based on Fermat’s Little Theorem), then this problem would have been MEDIUM and not EASY.
Besides this small issue with my own problems, the only really big issue I have to point to the contests, is the way the tester’s and/or setter’s tend to classify the problem difficulty levels.
For instance, we are told, while setting problems, to send an e-mail with our thought difficulty level and the problem requisites, possibly even BEFORE the problem is selected.
This is not good.
This is not good because a problem I can see as being MEDIUM or HARD can easily be seen as SIMPLE or even CAKEWALK by the given month’s tester.
Since the problems must be previously selected by taking into account the difficulty level we thought about (at least on an early stage), this opens room for a lot of ambiguity on the problem difficulty level classification.
I think that if we can have a better problem selection method based on the problem difficulty, than we can have more balanced contests…
(This will also eventually matter for the Tester him/herself, as if a tester is more experienced than other, he/she can have different points of view on the difficulty levels)