### McDic's blog

By McDic, history, 6 days ago, ,

안녕하세요, 코드포스! (Hello, Codeforces!)

I'm super happy to introduce you to Codeforces Round #566 (Div. 2), which will take place on Jun/11/2019 16:05 (Moscow time).

The round will be rated for all Division 2 participants, yet any Division 1 participants are welcome to join us out of competition.

You will be given 6 problems and 2 hours to solve them. Score distribution will be announced later.

The listed handles below are contributors. Thank you for all who listed!

This is my first Codeforces contest ever. I hope everyone who will join this contest enjoy. Thank you!

WINNERS:

1. Let me spread the meme from McDic Minecraft Telegram group — Ggungah.
2. Score distribution is 500-750-1250-2000-2250-2750.
3. Editorial is available.
4. Congratulations for the winners!
5. I am sorry for weak systests for B and F. Sorry again.

• +511

 » 6 days ago, # |   +8 Auto comment: topic has been updated by McDic (previous revision, new revision, compare).
 » 6 days ago, # |   +53 Best of Luck for your first contest as a problemsetter.
 » 6 days ago, # |   +88 Wa! A Korean round!
•  » » 3 days ago, # ^ |   0 :fan:
 » 6 days ago, # |   +69 upvote if you believe there will be kpop tasks in his korean contest
•  » » 6 days ago, # ^ |   -26 that will be wonderful(P.S BTS ARMY)
•  » » 5 days ago, # ^ |   +4 Listen to twice while solving twice problems.skill 1000
•  » » » 5 days ago, # ^ |   +19 listen to twice twice while solving twice problems twice.skills 1000000007
•  » » » » 5 days ago, # ^ |   +19 mod 1e9+7
 » 6 days ago, # |   -8 Hit you with that ddu-du ddu-du du~
 » 6 days ago, # |   +23 I wish everyone high rating!
•  » » 5 days ago, # ^ |   +12 Excellent tester for Excllent Contest ㅇㅅㅇ
•  » » » 5 days ago, # ^ |   +9 Yes, he is. ㅎㅅㅎ
 » 6 days ago, # |   -8 Korean round will be amazing!!!Oh my my my, oh my my my! I've waited all my life. Oh my my my, oh my my my! Looking for something right:)
 » 6 days ago, # |   +164 Why Hello is 안녕하세요 but Codeforces is 코드포스 which is shorter than Hello?
•  » » 6 days ago, # ^ |   +60 Also thought how difficult is it to write just "Hello", just unbelievable
•  » » 6 days ago, # ^ |   +58 That's not even a Hello.It's a Hi. XD!
•  » » » 5 days ago, # ^ |   +10 The other side is that Hi is longer than Hello! xD여보세요 : Hello안녕하세요 : HiGoogle Translate
•  » » » » 5 days ago, # ^ | ← Rev. 2 →   0 And 'Hello' can be used as both '여보세요' and '안녕하셰요' in my country, so It is also able to say the length of 'Hello' and 'Hi' is equal. :)
•  » » » » 5 days ago, # ^ |   0
•  » » 6 days ago, # ^ |   +25 I have always wondered how Chinese/Korean people write things
•  » » » 6 days ago, # ^ | ← Rev. 2 →   +34 That's an art :D(However I have not mastered it yet. T_T)
•  » » » 6 days ago, # ^ |   +93 It is actually very simple. We have these Oriental supernatural psychic abilities to inscribe complex letters into paper without using hands.
•  » » » 5 days ago, # ^ |   +11 I wonder how Arabs too
•  » » » » 5 days ago, # ^ |   0 Nope writing Arabic is easy.Arabic alphabets are simple in shape.
•  » » » » 5 days ago, # ^ |   +2 No, I'm Iranian and our font, Persian or Farsi is like Arabic. I think it is easy. :DMaybe these different opinions are because of different viewpoints. For us Korean or Chinese are hard to understand. But now I see that you think Arabic is difficult. Because we all are used to our own languages and other ones seem strange. But the most important think is that all languages are beautiful. :DSorry for my bad English. :DBtw do you Korean think your language is hard? Maybe I'm wrong.
•  » » » » » 5 days ago, # ^ |   0 Though I write Chinese since I born, I still think writing it is a exhausting job, lol.
•  » » » » » 5 days ago, # ^ |   +39 Korean letter seems scary because one syllable is cracked into a single letter. However, it's actually a composition of consonant letters (ㄱㄴㄷㄹㅁㅂㅅㅇㅈㅊㅋㅍㅌㅎ) and vowel letters (ㅏㅑㅓㅕㅗㅛㅜㅠㅡㅣ). So while there are 11172 Korean letters, you only have to remember 24 simple letters- after then you can write all of them!Korean people are proud of their language, and we have a "language day" which recently became a holiday. I also think this unique system makes pronunciation much clearer and complete. However, I'm not sure if it's easy, because "easy language" and "easy letters" are a different matter, and "smart letters" and "easy letters" also are. It's my mother tongue, so at least I'm not the one to judge.
•  » » » » » » 5 days ago, # ^ |   +3 Nicely said!
•  » » 6 days ago, # ^ |   +12 Technically it's Annyeonghaseyo XD
•  » » 6 days ago, # ^ |   +36 let's hope problems statements are long in Korean
•  » » 3 days ago, # ^ | ← Rev. 2 →   0 Well, if you use hanja honyong(漢字混用) to write 안녕하세요, the meaning of the phrase would be clearer (especially for Chinese). 안녕하세요=安寧하세요, it's asking if someone is free from worry. And, 코드포스=Kodeuposeu. This word is just a transliteration.
 » 6 days ago, # |   +9 Waa~~ It will be Good Good Round~~ :)
 » 6 days ago, # |   +4 korean round <3
 » 6 days ago, # |   +11 It will be good round :D
 » 6 days ago, # |   -6 How does it feel to have div2 after div3?
 » 6 days ago, # |   +11 BTS brought me here!!
 » 6 days ago, # |   +4 i hope there will be short questions !
 » 6 days ago, # | ← Rev. 2 →   -37 -Is it THE BEST div2 in the world? -No, Codeforves Round #566 Div2 THE BEST .Or -Is it THE BEST div2 in the world? -No, Codeforves Round #567 Div2 Was THE BEST
 » 6 days ago, # | ← Rev. 2 →   +57 "...Thank you all who listed!:- myself, arsijo- myself- arisjo- tester — [some testers and myself]- Mike"tm McDic
•  » » 6 days ago, # ^ |   +13 McDic orz
 » 6 days ago, # |   +11 Finally your round has arrived! Congrats! :D
 » 6 days ago, # |   -12 The contest has extra-registration?
•  » » 6 days ago, # ^ |   +3 Yes
 » 6 days ago, # |   +1 I hope a once wins your round :D
 » 6 days ago, # |   0 Unusual time for the contest, again
 » 5 days ago, # |   +2 I wish it will be a great contest . Thanks for this Effort
 » 5 days ago, # |   +40 ... and who is the mother? did cf and polygon got born by bipartition?
 » 5 days ago, # |   0 Happy ratings to everyone
 » 5 days ago, # |   +19 크으.. 국뽕에 취한다.. Cheer up McDic !
 » 5 days ago, # |   +3 I want to do last contest as a Specialist. -> Blue
•  » » 5 days ago, # ^ |   +4 Focus on the problems and worry less about your ratings, it will automatically follow :)All the best!
•  » » » 5 days ago, # ^ |   0 Yes! You are right.I will be trying my best.
•  » » 5 days ago, # ^ |   0 Deeply immersed by your curve :D
•  » » » 5 days ago, # ^ |   0 Sorry to say, My C failed due to my minor mistake.Hurt me a lot.I gave too much effort into C.
•  » » » 5 days ago, # ^ |   0 I think I will miss by +1 rating for becoming blue.
 » 5 days ago, # |   +14 sees a codeforces roundMe: Codeforces round yay!notices it's koreanMe: Codeuposeu round assa!
 » 5 days ago, # |   +5 BTS bring me here
 » 5 days ago, # |   -14 Is it rated up to 2100 rating like many other div2 contests?
•  » » 5 days ago, # ^ |   +1 Yes.
•  » » 5 days ago, # ^ |   0 what a typical question
 » 5 days ago, # |   0 Blackpink also cool)
 » 5 days ago, # |   0 Auto comment: topic has been updated by McDic (previous revision, new revision, compare).
 » 5 days ago, # |   +7 Maybe the reason for the unusual time of the contest is Iran vs South Korea soccer match! Korean want to watch the match to increase their confidence and rate in a contest. Wish a good game and a good contest too!
•  » » 5 days ago, # ^ |   +58 Or maybe Korean football players want to participate in their contest (;
 » 5 days ago, # |   +5 Let me fly up to Purple on gookbbong round~~~~~~~~
•  » » 5 days ago, # ^ |   +65 욱닥
•  » » » 5 days ago, # ^ |   -15 How could you say 욱닥 on comments??
•  » » » » 5 days ago, # ^ |   +49 욱닥
 » 5 days ago, # |   +36 Do you guys think doing a contest after anesthesia is a crazy idea?
•  » » 5 days ago, # ^ |   +5 Yes, it is a crazy idea
•  » » » 5 days ago, # ^ |   +3 Well let's see how much I can get negative rating.
•  » » 5 days ago, # ^ |   +2 i think it will be a great idea for me ,i won't feel the pain of my rating not increasing.
•  » » 5 days ago, # ^ |   +3 Guys, don't try this or you will end up competing with half-closed eyes xD
 » 5 days ago, # |   0 퍼플가게해주세요...(Let me go to Purple this round)
•  » » 5 days ago, # ^ |   +5 WOW! I really did!!
 » 5 days ago, # |   +53 Hmm. Why does nowadays always 6 problems? Is this only fast coding?
 » 5 days ago, # |   0 https://t.me/mcdic_chIf anyone needed link to his minecraft telegram channel...
•  » » 5 days ago, # ^ |   0 That channel is not used for a long time.. lol. I have active chat group now.
•  » » » 5 days ago, # ^ |   0 That is all what I found, sorry :DSo share your active chat group!
 » 5 days ago, # |   0 It seems that I haven't got the ability to solve problem D as it scored 2000. (smog
 » 5 days ago, # |   +29 Seeing the score distribution , i guess it is (speed + implementation) contest.
 » 5 days ago, # |   +4 hi team :)is the contest rated for div 3?
•  » » 5 days ago, # ^ |   +1 Absolutely
•  » » 5 days ago, # ^ |   0 Yes, of course
 » 5 days ago, # | ← Rev. 2 →   +57 That's why I love  ̶M̶a̶t̶h̶f̶o̶r̶c̶e̶s Codeforces
 » 5 days ago, # | ← Rev. 2 →   0 [deleted: irrelevant]
 » 5 days ago, # |   +15
 » 5 days ago, # |   +6 What an amazing implementation contest!
 » 5 days ago, # |   +13 In D why answer is not center of tree ?
•  » » 5 days ago, # ^ | ← Rev. 2 →   +5 check a look:41 2 2 33 4
•  » » 5 days ago, # ^ |   +8 Try this case: --- 8 2 1 1 3 3 4 4 5 1 6 6 7 7 8 --- The only answer is $2$.
•  » » » 5 days ago, # ^ |   0 so if the answer is not the center, then it must be one of the leaves right ? How to check that ?
•  » » » » 5 days ago, # ^ |   0 Suppose $v$ is not a center and not a leaf, then there are two leaves $l$ and $m$ at different distances from $v$ (suppose $l$ is closer). Consider the vertices at the same distance from $v$ as $l$ and notice that some of them are not leaves.
•  » » » » » 5 days ago, # ^ |   0 Ok thanks but I know how to prove that. What I want to ask is that if it is not the center, how could we find the leave which is the answer ?
•  » » » » 5 days ago, # ^ |   0 I tried to find centroid on slightly modified graph(I deleted chains starting from leaf nodes) I was late for about 30 sec to submit
 » 5 days ago, # |   0 How to approch E ?
•  » » 5 days ago, # ^ | ← Rev. 2 →   +6 The powers of f3, f2, f1 were terms of different tribonacci sequences with different first numbers. I couldnt figure out the sequence of powers of c, and it was also not there in OEIS :(Matrix Exponentiation is must, but couldnt figure out the matrix for c :'(
•  » » » 5 days ago, # ^ |   +6 Yeah, same ... wasn't able to figure out powers of c. Didn't know about OEIS though. Thanks for that :D
•  » » » » 5 days ago, # ^ |   -20 If you make $n=n-3$, then powers of c would be $2*\sum_{i=1}^n i = \frac{ n*(n+1) } {2}$
•  » » » 5 days ago, # ^ | ← Rev. 2 →   +3 You could reduce the problem to solving $G_{x} = G_{x-1}*G_{x-2}*G_{x-3}$, if you take $G_{x} = c^x F_{x}$. But, I couldn't see the fibonacci thing lol. Maybe we should have given the contest together xD.
•  » » » 5 days ago, # ^ |   0 Power for c was (n-2)*(n-3) using summation of AP formed: 2*(1+2+....(n-3)).
•  » » 5 days ago, # ^ | ← Rev. 2 →   +6 The answer is some power of $f_1,f_2,f_3,c$To deal with the power of $f_1,f_2,f_3$ it is a three-term recursion.(Fibonacci number is a two-term one). It can be rewritten in matrix form, and use fast power for large power.To deal with $c$ it is 2* A062544 in OEIS? It has a closed matrix form and solve it similar to the first one.Update 1 : Check tutorial/other stuff for better calculation of c
•  » » 5 days ago, # ^ |   0 Let g(x) = logc(f(x)) and h(x) = g(x) + x.The original equation becomes h(x) = h(x-1) + h(x-2) + h(x-3).After this, the problem could be solved by matrix power mod.
•  » » » 5 days ago, # ^ |   0 exponent " c " can be attached with f(X) to make it g(x) = (c^x)*f(x) ;
•  » » » » 5 days ago, # ^ |   +3 Yes. They look equivalent. I guess I am just not very comfortable with exponents.
•  » » » » » 4 days ago, # ^ |   0 I looked at your code https://codeforces.com/contest/1182/submission/55452776However, I was unable to understand the last 3 lines : ans = mul(ans, pow_mod(C, (3 * ll(a) + 2 * b + c) % (MOD - 1))); n %= (MOD - 1); ans = mul(ans, pow_mod(C, (MOD - 2) * n % (MOD - 1))); It would be great if someone could explain them!
•  » » » » » » 4 days ago, # ^ | ← Rev. 2 →   +1 Suppose after solving $h_x = h_{x-1} + h_{x-2} + h_{x-3}$ we end up with something like: $h_n = u\cdot h_3 + v\cdot h_2 + w\cdot h_1$.Therefore, $f_n = f_{3}^{u} \cdot f_2^{v} \cdot f_1^{w} \cdot C^{3u + 2v + w} \cdot C^{-n}$By Fermat's little theorem, we can take the reminder of the exponents mod $(MOD-1)$ to simplify the calculation.I hope this explains.
 » 5 days ago, # |   -11 As expected chinese and korean rounds are tooooo mathematical, btw good problems. how to solve d , e and F >
 » 5 days ago, # |   +3 how to solve C ??
•  » » 5 days ago, # ^ |   0 sorting first by the number of vowels, then alphabetically, on the one that ends, and then we create two arrays and run by the sorted, we look at the neighbors, if the letters are 2 words, then we sort again and see if the number of letters is equal, then it is 1 word. sorry, i don't know English very well.
•  » » » 5 days ago, # ^ |   0 huh! after implemeting c i went for hacks.. toooo messy .
 » 5 days ago, # |   +48 Shitty fast typing contest.
 » 5 days ago, # |   +55 I think in problem C finding m is enough and printing lyrics just makes problem complicated.
•  » » 5 days ago, # ^ |   -16 I dont think so, just create a map, work with indices and then print map[i], after finding M.
•  » » 5 days ago, # ^ |   +3 Yeah
•  » » 5 days ago, # ^ |   +2 yaa.... it's happened with me.
 » 5 days ago, # |   -6 How to solve E ??
 » 5 days ago, # |   +1 Any idea about pretest 16 in C? Is this logic wrong: For a given word,check if there is a word with same vowel count and same last vowel. If it isn't there,Try to check if there's something with same vowel count.
•  » » 5 days ago, # ^ |   +1 case: 4 a e e u
•  » » » 5 days ago, # ^ |   +4 holy crap. i should have run a pass first for finding all pairs with both vowel count and last vowel same,instead of doing both at the same time. changed that and your TC passes. Is this logic right? ^
•  » » » » 5 days ago, # ^ |   0 that's it
 » 5 days ago, # |   +41 C was devastating :))
•  » » 5 days ago, # ^ |   +3 B was literally devastating.
•  » » » 5 days ago, # ^ |   0 count me in
 » 5 days ago, # |   +3 Many submission will fail at problem B, i did 4 hacks and was close to 5th.
•  » » 5 days ago, # ^ | ← Rev. 4 →   +4 some hacks were single dot (.)single (*)and (*****)and .*.**..*.and5 10............*........******.*...*.................
•  » » » 5 days ago, # ^ |   0 And what the answers? it should be NO for all?
•  » » » » 5 days ago, # ^ | ← Rev. 2 →   0 answer will be NO
•  » » 5 days ago, # ^ |   0 Predicted OMG ^^
•  » » » 5 days ago, # ^ |   +1 hahaa.. even i went to hacking after first 3 problems as it was very hard to solved the remaining in remaining time. i did 4 hacks, submitted invalid input for 5th otherwise it would be 5. LOLOL..
•  » » » » 5 days ago, # ^ |   0 so st completed, so many many FST on B.
 » 5 days ago, # |   -6 C was tough for my current implementation level but I somehow managed to pass the pretests in the last minute of the contest lol
 » 5 days ago, # |   0 Auto comment: topic has been updated by McDic (previous revision, new revision, compare).
 » 5 days ago, # |   +114
•  » » 5 days ago, # ^ |   0 hhaha
 » 5 days ago, # | ← Rev. 2 →   +81 A: quite niceB: casesC: probably some cases too, didn't think of this taskD: quite an easy idea I think, shitty to implementE: mathsF: mathsI'm sorry, but I didn't find any of these tasks entartaining, very bad problem set (for me).
•  » » 5 days ago, # ^ | ← Rev. 3 →   +6 good analysis, though d was good. i think the problems were not learning oriented. I was expecting this, as it has became too common in chinese and korean rounds. even dp problems are like they r picked from some maths olympiad books.
•  » » 5 days ago, # ^ |   +3 I think D is so hard (sad)
•  » » » 5 days ago, # ^ |   +5 Is a nice problem though. I'm still thinking
•  » » 5 days ago, # ^ |   +13 first submit D, then talk! you made 9 attempts for D and still couldn't solve it! still a bad problem set FOR YOU?
 » 5 days ago, # | ← Rev. 2 →   -6 my code shows this output on C Idk why 2 that first the this mcdics about wow round edit:never mind stupid erase mistake
 » 5 days ago, # |   0 Thanks for fast editorials
 » 5 days ago, # |   0 Why my solution for C (id:55462095) wasn't judged when I submit at 01:59:45?
 » 5 days ago, # |   +15 RIP B
 » 5 days ago, # |   +16 B = hackforces
 » 5 days ago, # |   +12
 » 5 days ago, # |   +8 If honestly I don't understand. Pretests must be weak or this was just occasionally? I mean hacks like '.' and '*' and test 23 and so on. I understand that it is my fault but all in all pretests was too weak.
•  » » 5 days ago, # ^ | ← Rev. 2 →   +3 I asked them in the contest time about test only a * and they answered me its a invalid +, so if you were in doubt about this, you could have asked, even tho the pretest should have this test, I think.
 » 5 days ago, # |   0 How to calculate power of c in question E ?
•  » » 5 days ago, # ^ |   0 I think it is 2^(n-2) -2
•  » » » 5 days ago, # ^ |   0 For n=8 I calculated power of c as 60 and 116 for n=9
•  » » 5 days ago, # ^ | ← Rev. 3 →   0 According to me power of c was (n-2)*(n-3). I wasn't able to calculate powers of f2,f3 in time.Is power of c correct??
 » 5 days ago, # |   -14 What an unbalanced contest. Worst problemsetting ever.
 » 5 days ago, # |   +8 https://codeforces.com/contest/1182/submission/55446726O(TQ) solution passed in 31 ms
•  » » 5 days ago, # ^ |   0 what? hows that even possible?
 » 5 days ago, # |   +3 Seems like I have to give 2-3 contests to just come back to my original rating now :(
 » 5 days ago, # |   +3 its a time to be expert ^^
 » 5 days ago, # |   0 E and F was math problem. I think that F was pretty good, because there isn't many Trigonometry Problems
 » 5 days ago, # |   0 What is the test case 23 in div 2 B . My submission is fail on it test case 23 https://codeforces.com/contest/1182/submission/55452743
•  » » 5 days ago, # ^ |   0 Only one "*"
•  » » » 5 days ago, # ^ |   0 There should be atleast" +" symbol it neans all upward down left right and middle should be filled..so how single star??
•  » » » » 5 days ago, # ^ |   0 A "+" shape is described below:A "+" shape has one center nonempty cell. There should be some (at least one) consecutive non-empty cells in each direction (left, right, up, down) from the center. In other words, there should be a ray in each direction. All other cells are empty. Find out if the given picture has single "+" shape.This is what a + is, so, it s not obligated to have a + shape in the input, and that is why you have to code to find if there is only one + shape in the input, are you kidding me?
•  » » » » » 5 days ago, # ^ |   0 Alteast one is each side is written...so how single star?
•  » » » » » » 5 days ago, # ^ |   0 dude, can you talk private? i wana help you
•  » » » » » » 5 days ago, # ^ |   0 ur solution fails in :5 10............*........******.*...*.................answer should be no
•  » » » » » » 5 days ago, # ^ | ← Rev. 3 →   0 Even I coded the same logic as you. It will fail this case:-5 3.*.***.*.....*.Answer should be NO but your code will print YES
•  » » 5 days ago, # ^ | ← Rev. 3 →   0 It is something like that : 6 5.......*...***...*.........*..Answer is "NO".
 » 5 days ago, # |   0 Can someone check what's wrong in this solution for C? https://codeforces.com/contest/1182/submission/55451525
 » 5 days ago, # |   +10 In problem E, I am facing a doubt: I initially thought that I can condense the problem to the powers of f1,f2 and f3(ignore the c power for now). The powers of f1,f2 and f3 will be the nth, (n-1)th and (n-2)th term of Tribonacci sequence. But the powers will be in form of mod(10e9+7). As we know (a^b)mod M != (a^(b%M))%M ex: a=2,b=5,M=3, how do i effectively get the answer?
•  » » 5 days ago, # ^ |   +22 (a^b)mod M == (a^(b%(M-1)))%M for prime M, see Fermat's little theorem and Euler's theorem for general case.
•  » » » 5 days ago, # ^ |   0 Oh, Didnt knew this property. Thanks :)
•  » » » 5 days ago, # ^ |   0 ashmelev thanks!
 » 5 days ago, # | ← Rev. 2 →   +3 For test case 35 of problem B My compiler gave a 'NO' but codeforces custom invocation is giving 'YES' and I think I handled the case on which it is failing.here is my submission:Can someone please tell me why is this happenning?
•  » » 5 days ago, # ^ | ← Rev. 3 →   0 The problem is in your last two loops, it accesses invalid addressfor(ll j=0; j<=m; j++) ( it should be j
 » 5 days ago, # |   +3 Can you check my idea for solving "E"? In my point of View we can calculate degrees of F1, F2, F3, C F1's degree is Fib(n)F2's degree calculates by: F(1) = 1; F(2) = 2; F(3) = 3; F(n) = F(n — 1) + F(n — 2) + F(n — 3) F2's degree equal to F(n);F3's degree calculates by: F(1) = 1; F(2) = 2; F(3) = 6; F(n) = F(n — 1) + F(n — 2) + F(n — 3) F3's degree equal to F(n);C's degree calculates by: F(1) = 2; F(2) = 6; F(3) = 14; F(n) = F(n — 1) + F(n — 2) + F(n — 3) C's degree equal to F(n) + (2 * n — 6)Is my solution right? I got problem with Fast Computing "Tribonachi's"
•  » » 5 days ago, # ^ |   +1
•  » » » 5 days ago, # ^ |   +3 Thanks (Спасибо)
 » 5 days ago, # |   0 anyone can help me ? my code in problem B get wrong on test 23 But i test it locally and i get it OK
•  » » 5 days ago, # ^ |   +1 With what?
•  » » 5 days ago, # ^ |   +1 Test 23 has only one "*", are you outputing "NO"?
•  » » » 5 days ago, # ^ |   0 I copy test 23 and run in my code and get "NO"
•  » » 5 days ago, # ^ | ← Rev. 3 →   +1 case: 5 5.......*..*.*.*..*.......answer is "NO",but you get "YES".
•  » » » 5 days ago, # ^ |   0 5 5 ..... ..*.. ..*.. ..*.. .....your test is ? if it is , i test it locally and get it yes
•  » » » » 5 days ago, # ^ | ← Rev. 2 →   +1 try this one : ans will be no bt ur sol is giving ys.5 10............*........******.*...*.................
•  » » » » » 5 days ago, # ^ |   0 thank you very much .
 » 5 days ago, # |   +5 Congratulation to puyu_liao
 » 5 days ago, # |   -24 Make it unrated
•  » » 5 days ago, # ^ |   +3 Its impossible. There werent any technical problems on CF during the round
 » 5 days ago, # |   +20 For E,I have an idea.It's easy to calculate the power of f1,f2 and f3.I have a way to calculate the power of c easily. The transfer matrix:0 0 1 0 01 0 1 0 00 1 1 0 00 0 1 1 00 0 0 1 1By using this,we can change [a,b,c,d,e] into [b,c,a+b+c+d,d+e,e]The formula of the power of c is f[i]=f[i-1]+f[i-2]+f[i-3]+2*i-6Let a=f[i-2],b=f[i-1],c=f[i],d=2*i-6,e=2So now we can transfer it.The initial matrix is [0,0,0,2,2],because f[1]=f1*(c^0),f[2]=f2*(c^0),f[3]=f3*(c^0).
•  » » 5 days ago, # ^ |   0 And sorry for my poor English.
•  » » » 4 days ago, # ^ |   0 Thank you, understood well enough.
 » 5 days ago, # |   -23 It was what I worried about. If my country's users set problems for the first time and there was some factors that can be issue, next time my country's (other) users set second problems, people won't expect much.
•  » » 5 days ago, # ^ |   +21 For your information, I am not the first Korean problemsetter.
•  » » » 5 days ago, # ^ |   -6 I see. Anyway, because it's been a long time since there was Korean problemsetter, more prudence should have been.
•  » » » » 5 days ago, # ^ |   +24 Please don't care much about problemsetter's nationality. There are many good Korean problemsetters and I believe community care enough about them.
•  » » » » » 5 days ago, # ^ |   0 your problem set was nice enough
•  » » » » » » 5 days ago, # ^ |   0 I, didn't emphasized the problems' quality. And the quality of these is good. The sad thing is weak pretests.
•  » » » » » » » 5 days ago, # ^ |   0 Ya, luckily I passed problem B
•  » » 5 days ago, # ^ | ← Rev. 2 →   +14 ainta and .o. set the best Codeforces Round in the history of Codeforces ever, so it's OK.On a serious note, I think the round was nice. B is cool for Div2. D is quite interesting with strong pretests. Difficulty distributions are bit flawed, but it's fine if D/E was swapped, and you can see scoreboards anyway. (I actually didn't liked problem F, because one can just copypaste NAIPC 2019 D and play with some stupid binary search. but the model solution was easier, and I think it's not an issue for 99% of participants..)In the end, difficulty distributions are not something setter can guess correctly, and interesting problems are much more important. For every CF round, there is someone complaining about pretests and distributions, I just advise to ignore them :)
•  » » » 5 days ago, # ^ |   0 I, also want to think that way, but since that contest was over before more than 4 years, and since that there was no contest in which Korean was main problemsetter, for users joined after that contest this was like the first Korean problemset contest. It is also true that there are still many chances.
 » 5 days ago, # |   +1 Well balanced problem set, nice.
 » 5 days ago, # | ← Rev. 3 →   +3 problem c: is it valid? this first wow i .
 » 5 days ago, # | ← Rev. 2 →   0 how to sove D?
•  » » 5 days ago, # ^ | ← Rev. 2 →   0 i an not sure
 » 5 days ago, # |   0 Can anyone provide me a clear explanation on D? I thought many things non of them worked properly/on-time.
 » 5 days ago, # |   +3 Guys, what is the time complexity of rating changes calculation? Why does it take so long? Can't wait already =)
•  » » 5 days ago, # ^ | ← Rev. 2 →   +8
 » 5 days ago, # | ← Rev. 3 →   +3 E can also be solved using Reeds Sloane Algorithm(extension of BM for non-prime modulo). Link
 » 5 days ago, # |   +3 Test case is weak for problem C, there is no case present in the systests where no. of vowels of a string is more than 100000. I used that number as an array index in some part of my code, got AC even after I miss sized the array.
•  » » 4 days ago, # ^ |   0 Exactly. In my solution too I used an array of 100000 for storing the strings with number of vowels. I was sure that my solution would fail at system testing. I was shocked to see it passing. So yeah, Weak Test Cases For Problem C.
•  » » 4 days ago, # ^ |   0 I'm sorry about issue.
 » 5 days ago, # |   +8 Anyone who can take a look at my solution for E? 55469911I have no clue why it passed on small range input but failed on the bigger ones.
•  » » 4 days ago, # ^ |   +3 You should calculate exponent modulo phi(MOD) which is MOD-1 in this case.
•  » » » 4 days ago, # ^ |   0 Thank you very much!
•  » » 5 days ago, # ^ |   +2 "I was using it for past 3 contests and nothing wrong had happened before" Good that it happened to you now. Now you will never use ideone.
•  » » » 5 days ago, # ^ |   +1 It is fine to use it if you have private mode enabled.
•  » » » 5 days ago, # ^ |   0 Why aren't earliest submissions only accepted in case of plagiarism?
•  » » » » 5 days ago, # ^ |   +1 Because someone can copy the code from ideone and submit it faster than the original author.
•  » » » » » 5 days ago, # ^ |   0 True
•  » » » 5 days ago, # ^ |   0 True, I should've payed attention but it's unfair to be punished because of others' malevolence.
•  » » » » 4 days ago, # ^ |   0 The world is not fair.You may as well get used to it.
•  » » » » 4 days ago, # ^ |   0 You are getting punished for your carelessness as well.
 » 4 days ago, # |   0 Why was I skipped in Codeforces Round #566 (Div. 2), but counted rating.HELP！HELP！HELP！
•  » » 3 days ago, # ^ |   0 LOL
•  » » 3 days ago, # ^ |   0 copy code?
•  » » » 3 days ago, # ^ |   0 yes
 » 4 days ago, # |   0 I wonder if there's a solution for D using tree hashing, which I tried but failed.
 » 4 days ago, # |   0 shit. load shedding caused my specialist dream.
 » 4 days ago, # |   0 Really good and imaginative problems!
 » 4 days ago, # |   0 stupid Solution for D: There are two possible types of vertexes, corresponds with the statements of the task:1. One of the leaves2. Vertex in the "middle" of the tree. If there is only 2 vertex -> answer 1If there is only 2 leaves -> answer is one of them First of all, let's run bfs from each of leaves, and mark all the vertexes with their depths.(depth[leaf] = 0, depth["middle"] is the maximum). Now, if vertex with maximum depth is unique, lets check it.After, we need find one vertex with degree greater then 2 (it is always exist because of quantity of the leaves). Run bfs2 from it.////Let's define nearest vertex with degree greater then 2 for current vertex like a good.In this bfs, we need mark all vertexes by the pairs = {distance(current vertex, good vertex), index of the good vertex}.It easy to proof, that if answer is possible, than there is only one leaf with unique pair {distance to its good vertex, quantity of leaves that correspond for this good vertex}. Now we just need to check this leaf.code: 55487910
 » 4 days ago, # | ← Rev. 2 →   0 Why is my code for E giving wa on test case 5? Got the error ignore.
 » 4 days ago, # |   +19 weak tests for Dtest91 22 33 44 52 64 73 88 9answer should be 9https://codeforces.com/contest/1182/submission/55494688 gets AC but it shows -1 for this case.
•  » » 4 days ago, # ^ | ← Rev. 2 →   0 OMG I am really sorry about that. I handled almost ten type of trees and it was not enough.. :(UPDATE: Added that test in data
•  » » 4 days ago, # ^ |   0 I added that data and rejudged your case. I will try to find the way to rejudge all other's unofficial submissions. Thank you.
 » 4 days ago, # |   +8 Regarding question C during the contest I submitted first one Then I found a small mistake and changed it to second one. If you compare both submissions the change was a variable n for a constant value. It was accepted, but then just out of curiousity I resubmitted my first submission third one you can compare it with my first one and it is literally the same, and I got AC with this.However this is clearly wrong I mean you can test it with a small case ( 4 aaaaa aaaaa aaaaa aaaaa) My first and third submissions return 0 which is wrong and my second one returned 1 which is correct. So I'm not complaining about the fact that I lost points by fixing something that was wrong but would have been accepted anyways, I'm just wondering maybe the test cases are really weak or not good enough.
•  » » 4 days ago, # ^ | ← Rev. 2 →   0 I am so sorry about it. I should try so many various selections...UPDATE: Added that test in data
 » 44 hours ago, # |   0 Let's try our best!