Ccc 2012
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crossley7

Posted: Tue Feb 28, 2012 7:29 pm Post subject: RE:Ccc 2012 


I think that there are n! possible permutations so if n<5 then it would be
1!+2!+3!+4! = 33 possible starting positions with 3 of them being easy to solve. I won't go into more detail there because I think we are still supposed to wait on posting any solutions for longer (some people will have to write tomorrow or something) try not talking about problem specifics right now until we know it is ok to discuss 





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DanielKang

Posted: Tue Feb 28, 2012 7:31 pm Post subject: Re: RE:Ccc 2012 


RandomLetters @ Tue Feb 28, 2012 7:20 pm wrote: How did you manage to play 33 towers of hanoi games in under 3 hours?
There is some speculations, but i cannot say because we are not yet to discuss. 





Mamick

Posted: Tue Feb 28, 2012 7:42 pm Post subject: Re: Ccc 2012 


My teacher marked everyone's an I got perfect, though it hasn't been confirmed by Troy yet. I do agree with everyone else though that S4 was the hardest. My program would have failed for n=8 and above, and it took about a second for the n=7. Every other question was pretty trivial in my opinion.
I really hope the cutoff is below 55 so other people from my school can make it. Wasn't it about there a few years ago? 





chengbin

Posted: Tue Feb 28, 2012 7:49 pm Post subject: Re: Ccc 2012 


Are they trying to make the cutoff a perfect score this year???
1, 2, 3, and 5 were trivial. I was fairly close to solving 4. There has to be at least 20 people in Canada that can get S4 perfectly. It is not terribly hard, just tedious to code. 





crossley7

Posted: Tue Feb 28, 2012 7:50 pm Post subject: RE:Ccc 2012 


It will be over 60 because of the difficulty. The last few years the problems have been easier (this year + last year) allowing much higher marks and therefore a higher cutoff. Also, I thought time limit was something like a minute (no idea why) which would allow for alightly weaker solutions. As it is, that still cutoff the most naive solutions for #4. Last year 54 was the lowest score for honourable mention and this year the problems were arguably easier than last year meaning that sub 55 score definitely won't make it on. Once we can post solutions, I would love to see how you solved #4 Mamick. 





chengbin

Posted: Tue Feb 28, 2012 7:55 pm Post subject: RE:Ccc 2012 


This year is really unfair for the good programmers. If S4 is not your type of question, which is a really bad exercise in recursion, then you're not making stage 2. There should be at least 2 really hard questions so the cutoff a near perfect score. 





Mamick

Posted: Tue Feb 28, 2012 7:57 pm Post subject: Re: Ccc 2012 


I actually wasted about half an hour because I thought it was n<=8, but then I reread the question.
I feel that this year's was harder than last year's. In my opinion S1 was harder, S2 was about the same, S3 was about the same (though less tedious), S4 is about as hard as S5 from last year, and S5 requires more knowledge than S4 last year (though less logic is needed). 





DanielKang

Posted: Tue Feb 28, 2012 7:57 pm Post subject: Re: Ccc 2012 


chengbin wrote:
This year is really unfair for the good programmers. If S4 is not your type of question, which is a really bad exercise in recursion, then you're not making stage 2. There should be at least 2 really hard questions so the cutoff a near perfect score.
? That didn't make sense. 





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crossley7

Posted: Tue Feb 28, 2012 8:04 pm Post subject: RE:Ccc 2012 


I felt that s1 and s2 were trivial both years so just discounted them, s3 was a bit easier than last year, s4 this year and s5 last year are comparable and s5 a bit easier than s4 was last year. Again that is my opinion on it, but that is also probably partly because I have an extra year of coding and so I pick up the problems a little bit quicker.
And yeah, it kind of sucks that if you struggle with using recursion at all (like I do) then you are in for a challenge to make it to round 2 this year. 





chengbin

Posted: Tue Feb 28, 2012 8:06 pm Post subject: Re: Ccc 2012 


DanielKang @ Tue Feb 28, 2012 7:57 pm wrote: chengbin wrote:
This year is really unfair for the good programmers. If S4 is not your type of question, which is a really bad exercise in recursion, then you're not making stage 2. There should be at least 2 really hard questions so the cutoff a near perfect score.
? That didn't make sense.
You have to get perfect to make stage 2 since 4 of the problems are trivial. What if it is an insane ad hoc problem (which is the case this year) that you just can't get? As a senior contest, where are the true computer science problems involving hard dynamic programming, recursion, graph theory or computational geometry that I like (actually I don't like graph theory)? 





Mamick

Posted: Tue Feb 28, 2012 8:10 pm Post subject: Re: Ccc 2012 


chengbin @ Tue Feb 28, 2012 8:06 pm wrote: DanielKang @ Tue Feb 28, 2012 7:57 pm wrote: chengbin wrote:
This year is really unfair for the good programmers. If S4 is not your type of question, which is a really bad exercise in recursion, then you're not making stage 2. There should be at least 2 really hard questions so the cutoff a near perfect score.
? That didn't make sense.
You have to get perfect to make stage 2 since 4 of the problems are trivial. What if it is an insane ad hoc problem (which is the case this year) that you just can't get? As a senior contest, where are the true computer science problems involving hard dynamic programming, recursion, graph theory or computational geometry that I like (actually I don't like graph theory)?
I would just like to say that I've never seen a problem anything like S4 before, yet I still managed to get it. I do agree that the other problems should be harder, or there should be more (difficult) questions. 





RandomLetters

Posted: Tue Feb 28, 2012 8:11 pm Post subject: RE:Ccc 2012 


I thought S4 last year was not that hard (although incredibly tedious). I didn't get S4 and S5 at all this year though.
It would have been nice to see a more uniform progression in difficulty though, rather than 3 questions which everyone gets, and 2 questions which most people simply frustrate over 





102897108

Posted: Tue Feb 28, 2012 8:14 pm Post subject: Re: Ccc 2012 


chengbin @ Tue Feb 28, 2012 5:06 pm wrote: DanielKang @ Tue Feb 28, 2012 7:57 pm wrote: chengbin wrote:
This year is really unfair for the good programmers. If S4 is not your type of question, which is a really bad exercise in recursion, then you're not making stage 2. There should be at least 2 really hard questions so the cutoff a near perfect score.
? That didn't make sense.
You have to get perfect to make stage 2 since 4 of the problems are trivial. What if it is an insane ad hoc problem (which is the case this year) that you just can't get? As a senior contest, where are the true computer science problems involving hard dynamic programming, recursion, graph theory or computational geometry that I like (actually I don't like graph theory)?
S4 is a "true computer science problem" and anyone that qualifies for stage 2 should be able to solve that without too much struggle 





ihsh

Posted: Tue Feb 28, 2012 8:15 pm Post subject: RE:Ccc 2012 


I think 1 and 2 are perfectly fine as they are (trivial).
S3 is easy. It really doesn't require too much thought.
S4 is difficult compared to previous years; I had solved every S4 except the one from 2010 and this one.
S5 is definitely too easy; it's more like a S3 problem. There isn't really even a need to be efficient because of the small bounds. 





bbi5291

Posted: Tue Feb 28, 2012 8:21 pm Post subject: Re: Ccc 2012 


chengbin, based on experience, I highly doubt that 20 contestants will get full marks on S4.
The cutoff is not going to be a perfect score.
Bright contestants usually overestimate the cutoff, because they expect everyone else to find the contest as easy as they do.
S4 is not "a really bad exercise in recursion"; it has a straightforward solution. But even if it were, it should be pointed out that the early IOIs were full of such kinds of problems. 






