Codeforces Round # 759 was weird. Problem F was taken from Atcoder Regular 115 without any changes and problem D could be found in two places: Kattis and Codechef.
As was recently found, also test for F were very weak. This solution easily passes all test on round, but gives TL-es on atcoder.
This way, I don't really think this round should be rated, because the Statements represent more googling than thinking skills.
Pls express your opinion in comments
How did you add gif?
Even you didn't participate in the contest.
Completely agree, but the matter is not only in problem F. Problem D is also not original problem, it is well-known theorem, that permutation can be represented as composition of 3-cycles if and only if it is even, and the task is "Can we sort array using 3-cycles?"
So this round contains unbalanced(not so difficult and not original) problem D, and bad prepared and not original problem F, where $$$O(n^2)$$$ solution can pass.
This round definitely should be unrated.
do u have a blog on problem D, more specifically the theorem u mentioned here
No, but I think it is good idea to make blog about permutations, so I will make it soon. I will also put some general stuff about permutations, so don't miss it.
OK
$$$\sigma(a \cdot b) = \sigma(a) \cdot \sigma(b)$$$, where $$$\sigma$$$ is a sign of permutation. ($$$\sigma(x) = \pm 1$$$)
No, I guess the authors didn't even know the existence of that problem. Unfortunately, the probability of coming up with an already used problem is quite high. I invented at least $$$6$$$ problems that turned out to be already on the Internet.
Really? They wrote the same statement without knowing about ARC 115. Do you believe in it? And do you really believe KAN didn't know about existence of it? There is even the same modulo!
Just to make all things clear, this modulo is kinda default, because it can be used in FFT(some people call it NTT). $$$p = 7 \cdot 17 \cdot 2^{23} + 1 = 998244353$$$, but in Russia problemsetters use $$$10^9 + 7$$$ more often than $$$998244353$$$
But problem F has exactly the same statement as problem from Atcoder. The chance of this to happen....
That's the most reasonable way to write that statement. The chance of this to happen is $$$50\%$$$.
Normally I wouldn't agree to make a round unrated, but if this is really the case, then it should become unrated indeed.
Do you really think the red coders who solved D and F rely on google to come in the top 100?
The red coders remember that F was in AtCoder without googling.
(By the way I'm sure that D is even more well-known because it sounds like a common group theory homework.)
Haha, I recognized that it was an old Atcoder problem (and the many/fast solves made me think it was a repeat). But I tried to find it and I couldn't.
If you used the time you wasted trying to find the problem on AtCoder, In solving this problem, you could have solved it!
you always reply to my comments
UPD: + ratio
From now on I'll make sure to google every problem before trying it.
That's a very bad practice to improve your problem-solving skills.
i was being sarcastic
besides my horrible contest, the fact that D and F both were copied id not fair for thr participants. I dont know about unrated .But recently the quality of contests on codeforces has been declining . I mean , recently only there were many contest which had directly copied problems. And to the argument that the testers didnt knew. How can the problem statemnt be exactly same, in some of them even the name of the fictional charcaters and many thing word by word , proposition by proposition is same. What do we rather petition for is mainting the standard of contests which used to happen on codeforces .Copy pasted problems is not good for the community.
Even though the contest is ( maybe a bit extreme , rubbish ) , i think , that's not the reason to be unrated.
if this is really the case, then I think it's worth making the round unrated
This is not so fair to those who did well without googling. Besides, people who did google will likely lose rating on future contests so it isn’t so necessary to make the round unrated. Also, even if such problems were unoriginal that doesn’t necessarily make them not educational and of course at some point people will begin to run out of problem ideas and reuse old concepts.
Granted, I didn't take part in this round. But you seem to be claiming two things which are contradictory, or at least unlikely, depending on your interpretation.
As far as I can tell, you're arguing that the CF problem's tests are weak because there are stronger tests on the AtCoder problem. But you also claim that problem F was taken from AtCoder without any changes. The only way I can think of reconciling these statements is that you mean the author stole the problem idea but not the test cases. That is plausible but I find it unlikely. If we are already assuming the problem is stolen, why not steal the test cases too, or at least get ideas for the edge cases which will cause TLE?
There is certainly an argument that can be made that the problems were copied. But the specific argument present here doesn't seem to stand up, at least to me.
It's hard to find ARC115E with words in problem F, so I don't think it represent googling skills.However, I agree the round should be unrated because it's unfair for those who haven't seen ARC before.