Ok. I'll be fair and honest here. Prepare to be spoiled hard.
The contest :
At first i was like "this contest is amazing". I first had a "good and simple code" with a score of 80k. And i was still at this score 4 hours before the end of the contest. My code was just running on the furthest human i can save or the "killer zombie" if it's faster. Then the contest showed it's weakness. A bugged code can do far more point than a non-bugged code. A little frustrating ...
Then i took a shower. You all know this kind of shower. You are not here to clean yourself. You are here to think. Your mind is hotter than the water.
How i manage to end up at the 6th place with the score of 424k ? Spoiler alert : i cheated.
Oooh, i hear you from my chair : "how can you cheat in a contest like this ?" Very simple.
When i was under the water in my bathroom, i remembered the Bilbo contest. I don't remember who said that to me. But for the Bilbo contest, some of the top players used the same kind of cheat.
What is that cheat ? Guess the validators.
How some of top players at Bilbo were so high ? They guessed some validators (not all, but some of them). The reversed alphabet was easy to guess. Some were a little harder.
So, let's back to Code VS Zombie. 4h before the end, i was curious if it was possible to guess some validators. I think you all remember the 280k combo on the CG test case (the replay was on the chat). I hard coded it and i just reversed the y values. Jackpot. 360k points. I did the same for combo opportunity but this time i reversed the x values. Second jackopt, 424k points.
The optimization puzzle :
Before the contest, i talked to MaximeCG. I told him it will be very cool if validators will stay hidden forever. Because other optimization puzzles are more like "the best hardcoder win" (i'm not talking about codesize puzzles. Just bilbo and mars lander).
When the contest ended, i was all like "there's no reason to keep validators hidden if they are that easy to guess anyway ...". And now the optimization puzzle is here, and you know what ? I tried to guess some validators, unsuccessfuly at the moment. They are not just some symetrics or x/y shiftings. And this is a very very very good thing.
Monte Carlo codes :
I'm not sure how "Monte Carlo" codes should be handled during contest. Coding a monte carlo code is not that hard and make a tons of submits is not that fun too. But eldidou had the idea and won with it, no reason to blame him.
I don't know the CodinGame staff feelings on it. It is pretty easy to "block" this kind of codes. Just rerun the code at the end of the contest. But i don't know if it is a good idea.
Contest validators :
Please, make validators harder to guess. If i can guess the validators like that, i'm not the only one. The validators for the optimization puzzle are fine i think (because i can't guess them for now ). Optimization contests should always have validators like this.
Optimization validators :
I totally agree that optimization puzzles validators must be hidden. It was my suggestion to MaximeCG so i can only say it is a great idea ! But, can you re-think this for Bilbo ? At the moment, the Bilbo validators are hidden. But some of the players know them. It's unfair for new players (Mars lander don't have the problem since validators are the same that the IDE test cases).
Do i deserve my 6th rank ?
I don't really know. I feel like i cheated. But i know that this cheat was also possible for Bilbo. So if by this post i can avoid the same thing for future optimization contest, i will be very glad. Without that cheat, i would be at the 70th rank (or something like that).