### Ari's blog

By Ari, 3 years ago,

Hi!

On Jul/04/2020 17:45 (Moscow time) we will host Codeforces Global Round 9.

It is the third round of a 2020 series of Codeforces Global Rounds. The rounds are open and rated for everybody.

The prizes for this round:

• 30 best participants get a t-shirt.
• 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2020:

• In each round top-100 participants get points according to the table.
• The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
• The best 20 participants over all series get sweatshirts and place certificates.

Thanks to XTX, which in 2020 supported the global rounds initiative!

The problems of this round were prepared by a team of authors: adamant, antontrygubO_o, Ari, dengyaotriangle, hugopm, Kuroni, enoone, and Ynoi. We would like to thank the following people:

You will be given 2 hours and 30 minutes to solve 9 problems, and we highly encourage you to read all of them :)

To save testers the work of writing their opinion in the comments, we have compiled some of their opinions for them!

Round Feedback

Good luck!

UPD: Score distribution:

500 — 750 — 1500 — 1750 — 2000 — 2000 — 2250 — 2750 — 4000

UPD2: Editorial

UPD3: System tests have finished, congratulations to the winners!

Announcement of Codeforces Global Round 9

• +2693

| Write comment?
 » 3 years ago, # |   +3388 As a tester, give me contribution.
•  » » 3 years ago, # ^ |   +49 You are so honest. Otherwise, most of time tester tries to gain contributions by just commenting something shit....
•  » » » 3 years ago, # ^ |   +415
•  » » » » 3 years ago, # ^ |   +140 Now, this is the most upvoted comment after Is it rated?Full List
•  » » » » » 3 years ago, # ^ |   +26 so let's make it the most upvoted comment.
•  » » » » » » 3 years ago, # ^ |   +18 Now it became the most upvoted one. :)
•  » » » » » » » 3 years ago, # ^ |   +43 I'm so jealous =P.
•  » » » » » » » » 3 years ago, # ^ |   +5 U should be happy about it that the testers are getting more attention than the problem setters. :=)
•  » » » » » » » 3 years ago, # ^ |   +26 Everything is good and all but what's up with your handle tlsdydaud1
•  » » » » » » 3 years ago, # ^ |   +69 It is now the most upvoted comment !!1!!1!
•  » » » » » 3 years ago, # ^ | ← Rev. 2 →   +108 The comment has more upvotes than the blog.
•  » » 3 years ago, # ^ |   +177 The only thing I remember about Monogon is that his first ever contest after being such a beauty was ruined due to long queues and finally the round became unrated. Awaiting another round from you.
•  » » » 3 years ago, # ^ |   +4 He tested the last round too.
•  » » 3 years ago, # ^ |   +6
•  » » 3 years ago, # ^ | ← Rev. 2 →   -16 Sorry for that..
•  » » 3 years ago, # ^ |   +26 You are now in top 10 contributors. Cong!!
•  » » 3 years ago, # ^ |   +29 may be for the first time a tester is going to get more contribution than the setter xdneed 247 more only :P
•  » » » 3 years ago, # ^ | ← Rev. 5 →   -20 Sorry for that.
•  » » 3 years ago, # ^ |   +30 The most upvoted comment ever?
•  » » 3 years ago, # ^ |   +14 If only herd immunity was as easy as herd behaviour...... P.S. you have my vote.....
•  » » 3 years ago, # ^ |   +1 I hope Monogon prepares a round after gaining such support from the community. We will try to make the contest announcement blog the most upvoted blog on CF.
•  » » 3 years ago, # ^ |   -10 You have it, >2000 upvotes :D.
•  » » 3 years ago, # ^ |   +251 As the most upvoted comment in history, I think this proves that the greedy works.
•  » » 3 years ago, # ^ |   +1 Damn! Even, most of the "contest announcement" blogs have less upvotes.
•  » » 3 years ago, # ^ |   -7 Would it break the tourist's global round 5 record?
•  » » 3 years ago, # ^ | ← Rev. 2 →   +19 This has to be a record of some kind.
•  » » 3 years ago, # ^ |   +1 Can monogon's comment beat tourist's rating someday? =O
 » 3 years ago, # |   +125 AC Round #3
•  » » 3 years ago, # ^ |   +6 What is AC Round ?
•  » » » 3 years ago, # ^ |   +94 AC is a discord server for competitive programmers. Most of the authors/testers of this round are members of the server. This is the third round made by AC members, here and here are the first two rounds.
•  » » » » 3 years ago, # ^ |   0 how do u get the link for the server?
•  » » » » » 3 years ago, # ^ |   +59 this is the link.
•  » » » » » » 3 years ago, # ^ |   0 Thanks for the link :)
 » 3 years ago, # |   +208 This has to be one of the best contest announcement.
 » 3 years ago, # |   +25 I am not tester, but i strictly reccomend you to participate in this contest!
•  » » 3 years ago, # ^ |   +7 yes yes of course of course
 » 3 years ago, # |   -60 I'm a tester, and this round is very good.
•  » » 3 years ago, # ^ | ← Rev. 2 →   -8 Why am I getting downvoted? I'm stating my opinions as a tester.
•  » » » 3 years ago, # ^ |   0 Cause everyone saw that, you are not in the tester list :v
 » 3 years ago, # |   +119 As a participant, I need more time to recover from the previous contest.
 » 3 years ago, # |   +304 They stole my contribution =(.
•  » » 3 years ago, # ^ |   +49 Thanks for giving me contribution =).
 » 3 years ago, # |   +5 Ok then
 » 3 years ago, # |   +5 very comedically humorous Ari
 » 3 years ago, # |   +39 Is feedback meant for frightening us?
 » 3 years ago, # |   +48 As a participant, I am already scared
 » 3 years ago, # | ← Rev. 2 →   +204 Finally this day has came, a round with adamant as an author.
•  » » 3 years ago, # ^ |   +67 Oh god I was planning to join this round :(
•  » » 3 years ago, # ^ |   +92 Anal is short for analytic, right? ;)
•  » » » 3 years ago, # ^ |   +23 Yeah. He has given a lecture on this subject at mwj.
•  » » » 3 years ago, # ^ |   +25 you saved my mind from burning
•  » » » 3 years ago, # ^ |   +178 and oral is for oralytic
•  » » » » 3 years ago, # ^ |   +10 Bruh, obviously ORAL stands for Outstanding Requisition Analysis Report.
 » 3 years ago, # |   +3 thanks for the meme!
 » 3 years ago, # |   +18 The announcement just ensured that one more time we are gonna miss MiFaFaOvO vs tourist match.
•  » » 3 years ago, # ^ |   -12 Tbh, it looks more like ecnerwala vs tourist to me. Just an opinion tho.
•  » » » 3 years ago, # ^ |   -19 I don't get why you guys are more interested in tourist than yourself.Is that why you are green/cyan?
•  » » » » 3 years ago, # ^ |   0 I find inspirations seeing the success of some great coders so that i am interested about them.You better focus on your own success (as you are a colorless or a fake account).
•  » » » » » 3 years ago, # ^ |   +6 I hope notgonnalie is a human, not a colorless or a fake account...
 » 3 years ago, # |   -24 Glad a real CF round is coming,last round killed my spirit...
•  » » 3 years ago, # ^ |   -52 Hope this doesn't happen Spoiler...
•  » » » 3 years ago, # ^ | ← Rev. 2 →   +4 .
•  » » » » 3 years ago, # ^ |   0 Do you want to say anthing about this
•  » » » » » 3 years ago, # ^ |   +13 Yes I wasted a lot of time and truly it sucks . Moreover it made me realized that I should focus on solving problems instead of making memes. I had no intention of disrespecting you but only making letting you know about my mistake.
•  » » » » » » 3 years ago, # ^ |   0 Thanks for letting me know. I had no intention of disrespecting you too.
 » 3 years ago, # |   +9 As a participant, I am eager for tourist vs Um-Nik
•  » » 3 years ago, # ^ |   +18 That's rather as a spectator. You don't need to participate for that.
 » 3 years ago, # |   +27 tags: "doomsday" oof
 » 3 years ago, # |   +12 People trying to be sarcastic in comment section Problem Setters And Testers : Say No More Ps : Is it best announcement ever? :P
 » 3 years ago, # |   +116 amiya : " I'm happy sitting atop the CF rankings. You guys give the contest."
 » 3 years ago, # | ← Rev. 3 →   +69 You will be given 2 hours and 30 minutes to solve 9 problems, and we highly encourage you to read all of them :) Is this statement meaningful or is this general good advice for any round?
•  » » 3 years ago, # ^ |   +23 A :) in the end says it all.
•  » » 3 years ago, # ^ |   +29 I guess I should have read F earlier than I did!
•  » » 3 years ago, # ^ |   0 Looking your shirt more good now!!
•  » » » 3 years ago, # ^ |   0 Thanks!
•  » » » » 3 years ago, # ^ |   +1 Congrats on becoming Red.
 » 3 years ago, # |   +139 But man, by the time I understand 9 problem statements, 2,5 hour is already gone, and I already forgot 8 of them...
•  » » 3 years ago, # ^ |   0 Plus!
 » 3 years ago, # |   +9 As a russian guy, I don't understand tester's feedback.Joke
 » 3 years ago, # |   -27 Looks like it's going to be a difficult contest.
 » 3 years ago, # |   +220 "As a problemsetter, I am sorry" As a contestant,
 » 3 years ago, # |   +256 ......
 » 3 years ago, # |   +37 As a participant, I will participate.
 » 3 years ago, # |   0 Looking forward to the problems. The announcement is hilarious and I hope the problems will be as well.
 » 3 years ago, # |   +235
•  » » 3 years ago, # ^ |   -6 Never participated in Global Rounds. Are problem sorted by difficulty?
•  » » » 3 years ago, # ^ |   0 You can check Here all global rounds By yourself.
•  » » » » 3 years ago, # ^ |   +9
•  » » » » » 3 years ago, # ^ |   0 Now more helpful..Thanks..Is it your website brother ?
•  » » 3 years ago, # ^ |   +22 Better rightly write right.
 » 3 years ago, # | ← Rev. 2 →   +21 Don't worry, you guys are gonna enjoy the round :)
•  » » 3 years ago, # ^ |   -21 I also think that we will enjoy.
•  » » 3 years ago, # ^ |   0 You didn't add "as a tester". That's suspicious...
•  » » » 3 years ago, # ^ | ← Rev. 2 →   -20 [deleted]
•  » » » » 3 years ago, # ^ |   0 Learn how to determine the parent comment.
•  » » » » » 3 years ago, # ^ |   +8 Sorry for that..
•  » » 3 years ago, # ^ |   +11 unrate :aaeria:
 » 3 years ago, # |   +19 Probably, one of the best contest announcements.
 » 3 years ago, # | ← Rev. 4 →   -11 As a contestant, I quit.
•  » » 21 month(s) ago, # ^ |   0 mmkay bye!
 » 3 years ago, # |   +4 i'm confused, should we be playing or not?
 » 3 years ago, # |   +185 I see that I'm going to love this round...
•  » » 3 years ago, # ^ |   +94 No, you'll say that there is another platform for such contests
•  » » » 3 years ago, # ^ |   +106 To be honest, adamant and antontrygubO_o together as problemsetters give hope that we'll finally see some balance.But also the opposite is possible: that every problemsetter has just a position (A-I) assigned and all the problems will be chosen completely independently from the others and we'll finish having a 100% "another platform" contest.
 » 3 years ago, # |   -6 Hoping to become an Expert after this round :)
•  » » 3 years ago, # ^ |   +1 Good luck for you <3
 » 3 years ago, # |   +441 Do you want to get fewer participants with this anti-advertising of the problem set? If the goal is to avoid the server load, just say that there will be a lot of math in div2 problems.
•  » » 3 years ago, # ^ |   -15 LOL ! People will still try out of courage and for rating ! If it goes well they will be commenting like Best ProblemSet ever ! and if not they have their cliche MathForces
•  » » 3 years ago, # ^ |   +431 There are a lot of math in div2 problems.
•  » » 3 years ago, # ^ |   +37 Errichto It's been a long time since we saw you setting problems ! Come Back ! Soon ! :)
•  » » 3 years ago, # ^ |   +35 Even better, just say the whole round is Geometry
•  » » » 3 years ago, # ^ |   +249 the whole round is Geometry
•  » » » » 3 years ago, # ^ |   +41 I see what you did there
•  » » 3 years ago, # ^ | ← Rev. 2 →   -16 When you khow people scared with math then do you do something like tutorial on how to get well in math? Errichto
•  » » » 3 years ago, # ^ |   +8 I doubt that abundance of tutorials is going to cure aversion to "math".
•  » » 3 years ago, # ^ |   -14 I think. they r going for reverse psychology here....!!
 » 3 years ago, # |   -15 First time, I see meme in contest announcement.There must be a reason behind it. We should be aware of that.Good luck to everyone. :p
 » 3 years ago, # |   -34 How pupils become tester? :D
•  » » 3 years ago, # ^ |   -31 Racist
•  » » » 3 years ago, # ^ |   0 no u
 » 3 years ago, # |   +34 As a contestent, I want rating.
 » 3 years ago, # |   -10 xd
 » 3 years ago, # | ← Rev. 2 →   +2 Same story, again and again, my smoll pp skills and big pp problems.
 » 3 years ago, # |   -18 Best CF Round invitation ever =P
 » 3 years ago, # | ← Rev. 2 →   0 as a participant, i am also scared and i don't want to participate!) GL&HF to everyone!!!
 » 3 years ago, # | ← Rev. 2 →   0 ....
•  » » 3 years ago, # ^ | ← Rev. 2 →   +13 As a tester, My advice is to think 1 more day, because problems are more scarier than you are thinking...XD
 » 3 years ago, # |   +5 I don't know why but it is giving me vibes of an amazing round.
 » 3 years ago, # |   +167 .****
 » 3 years ago, # |   +7 9 Problems with an army of testers and 8 writers. Excited
 » 3 years ago, # |   -27 IT IS TAGGED DOOMSDAY!!!
 » 3 years ago, # |   0 New here, it is going be my first Global Round and the comments already scare me. Is it a good idea for a new guy to take part in it? or will it be discouraging?
•  » » 3 years ago, # ^ |   0 If you are new dont think of rating from the beginning try giving as many contest as you can. Thats what i learnt
 » 3 years ago, # |   +12 9 problem that's huge. I appreciate the hard work to make a contest.
•  » » 3 years ago, # ^ | ← Rev. 2 →   +1 Yes appreciate problem setters for these kind of contests
•  » » » 3 years ago, # ^ |   +41 "You will be given 2 hours and 30 minutes to read all of them." I think that's what he is trying to say.
 » 3 years ago, # |   -41 Links of previous global rounds:Codeforces Global Round 5Codeforces Global Round 6Codeforces Global Round 7Codeforces Global Round 8Hope this helps!
•  » » 3 years ago, # ^ |   -18 Appreciate your work but we can directly search any round and go to contest link in the announcement.
•  » » » 3 years ago, # ^ |   -8 The reason why it is not useful is probably not that "we can find it ourselves" but that this list was also shared in the previous global round. In fact, link to a web app was shared which can do this right away.
 » 3 years ago, # |   -16 This global round seems to be very special among all previous global rounds because of its awesome announcement!!
 » 3 years ago, # |   -7 I was going to make a century of losing rating in last contest...I think,this is another opportunity to complete the century...Shouldn't I be happy!!! SENTY_EMO
 » 3 years ago, # |   0 how is global round different from other rounds???
•  » » 3 years ago, # ^ | ← Rev. 2 →   0 [Deleted]
•  » » 3 years ago, # ^ |   0 you looks like topcoder
•  » » » 3 years ago, # ^ |   0 thanks
 » 3 years ago, # |   +12 As a contestant, I will take part in the contest. :)
 » 3 years ago, # |   -16 Can someone tell me what happened to static a2oj? I used to solve problems from there difficulty wise and now, instead of that a different website with that names comes and all the problems of the ladder are locked there.
•  » » 3 years ago, # ^ | ← Rev. 2 →   +1 Hey ,use this site .Works fine for me a2oj has been closed for some reason (https://earthshakira.github.io/a2oj-clientside/server/Categories.html) (https://earthshakira.github.io/a2oj-clientside/server/Ladders.html)
•  » » » 3 years ago, # ^ |   0 yeah it's working fine thanks a lot brother
•  » » » » 3 years ago, # ^ |   0 :)
 » 3 years ago, # |   +9 Finally, memes are on Contest announcement blog post :v
 » 3 years ago, # |   -11 Explain me the difference between Educational round and Global round in div 2 like contest there is time penalty what about Codeforces Global Round .Thank you.
•  » » 3 years ago, # ^ |   0 In Global round also every problem score decrease with time . It's almost like Div-2.
•  » » 3 years ago, # ^ |   +24 Global round is rated for everyone, educational round is rated for people who have rating less than 2100 Global round has some fixed points for each problem which reduces slowly as time goes on, all problem has equal points on educational rounds. Hacking runs parallel with contest in global round, there is hacking phase in educational rounds after contest finished. Wrong submission on finally accepted solutions will cost you 20 points in global round, in educational rounds it will cost you additional 10 minutes time penalty. On global round last pretest passed solution will be judged and resubmission will cost you 50 point and in educational rounds all pretest passed(accepted) solution will be judged and 1st solution that passed system test will be considered.
•  » » » 3 years ago, # ^ | ← Rev. 2 →   +2 How do you compare 20 points vs 10 minutes of penalty? What is the exact relation (if there exists one)?
•  » » » » 3 years ago, # ^ |   +21 I compare in sense of what will happen one submit a wrong solution.
 » 3 years ago, # |   0 thanks to all of them for frequent rounds
 » 3 years ago, # |   +7 Next round after the global round is one week later.Are we not going to have any round before that?
•  » » 3 years ago, # ^ | ← Rev. 2 →   +10 There are almost 2 educational and div3 rounds in every month.So probably we will be having both also if a contest is added for date x it does not mean mike can not add a contest which has date strictly lesser than x.
 » 3 years ago, # |   -9 A meme in the announcement .. you got my upvote
•  » » 3 years ago, # ^ |   -8 Hey Boss how to get like your meme idea.. I want to make my contribution 0.
•  » » » 3 years ago, # ^ |   0 the idea just flashes in my mind and I search for photos that can present the meme and edit it on paint I can give you an advice some of my memes goes this way you just compare 2 completely opposite situations like this one it's how I used to be when I started and how I'm like now this meme is actually sad for me XD or like this one it starts with someone asking them to be quite while it ends up with a party so there should be an element of surprise if it's something expected or usual then this is a bad boring meme and it should be about codeforces and competitive programming not jokes about html that's out of the context
 » 3 years ago, # |   +179 You will be given 2 hours and 30 minutes to solve 9 problems, and we highly encourage you to read all of them :) Problem I.You are given two integers a and b. Print a+b.
•  » » 3 years ago, # ^ |   +318 Don't spoil before the contest
 » 3 years ago, # |   +8 I am excited for the round..hope for the best
 » 3 years ago, # |   +5 dude that feedback gave me chill more than any meme xD xD
 » 3 years ago, # |   -24 WTH to me. i was going to attend the contest today at 20:35..
 » 3 years ago, # |   +87
 » 3 years ago, # | ← Rev. 2 →   0 I like this meme!
 » 3 years ago, # |   +6 I love the announcement """""D
 » 3 years ago, # |   -48 In problem B,can anyone explain this formula => a+(a+1)+(a+2)+...+b=(a+b)∗(b−a+1)/2 and what is it called
•  » » 3 years ago, # ^ |   0 Just subtract sum of first b natural no. From first a-1 numbers. Like b*(b+1)/2 — (a-1)*a/2
•  » » 3 years ago, # ^ |   0 Last contest B ??
•  » » 3 years ago, # ^ |   0
 » 3 years ago, # |   -18 I hope there are a few or no problems based only on observation
•  » » 3 years ago, # ^ |   -26 I hope a problemset like that of the previous round doesn't happen again. Problems A-D: Observation. A-C are 1 liners. D is two nested for loops which can be written with 3 lines. Problem F: Think for half a second, implement for half an hour.
 » 3 years ago, # |   0 In China, there is a well-known serie of huge datastructure problems called Ynoi.... Is it gonna have huge datastructures like ctholly tree?
 » 3 years ago, # |   +54 As a stupid American, I don't get the testers' jokes.
•  » » 3 years ago, # ^ |   +7 rotavirus OTZ
 » 3 years ago, # |   -21 As a participant, I have a hunch that I should hide my brain during the contest
 » 3 years ago, # |   -8 Excuse me. Can someone tell me how the round is rated? I mean: is it rated like div.1, div.2, or div.3? I'm not very familiar with the contests of CodeForces (as you can see I'm a Newbie). Thanks for helping!
•  » » 3 years ago, # ^ | ← Rev. 3 →   -20 Sorry for wrong... 
•  » » » 3 years ago, # ^ |   0 Alright. Actually I thought that it is rated in a way like div... but it seems that it's different. Thanks anyway.
•  » » » » 3 years ago, # ^ |   0 Yes different .. See this
 » 3 years ago, # |   -16 so here comes the DOOMSday
 » 3 years ago, # |   -20 For the first time, I am feeling nervous that something bad is going to happen with me in this round :(
•  » » 3 years ago, # ^ |   +3 and what are the good things that happened to you in any round till now
 » 3 years ago, # | ← Rev. 5 →   +5 Codeforces contests are like a sport for me . I enjoy the problem mostly without noticing my rating .
 » 3 years ago, # |   0 is this one as easy as div 2?
 » 3 years ago, # |   -74 tourist after reading round feedback
 » 3 years ago, # |   0 As a participant, I am scared.
•  » » 3 years ago, # ^ |   +70 As a scared, I am a participant.
•  » » » 3 years ago, # ^ |   0 May the (code)force be with you friend XD
 » 3 years ago, # |   0 how the contribution is calculated.
•  » » 3 years ago, # ^ |   +8 It works like the hippos, you have to effectively shed your territory.
 » 3 years ago, # | ← Rev. 2 →   +64 Ari Hey, I understand that you want to make a point, but don't you think tagging them is unnecessary? I believe noone likes to be tagged just to see themself being thanked every week.
 » 3 years ago, # |   0 GOOD LUCK TO EVERYONE!!!
 » 3 years ago, # |   +19 Out of curiosity, What's the record for the most downvotes? (Can this comment break that record? xD)
•  » » 3 years ago, # ^ |   +8 This might help.
 » 3 years ago, # |   +149 gamegame and dorijanlendvaj, for their help in improving the humor of the round.During round :
•  » » 3 years ago, # ^ |   +50 During round:
•  » » » 3 years ago, # ^ |   +8 knock knock
 » 3 years ago, # |   +7 Honestly, Is this contest suitable for a newbie????
•  » » 3 years ago, # ^ | ← Rev. 2 →   -14 Don't.tbh tho A and B solvable.
•  » » » 3 years ago, # ^ |   0 Need to learn a lot. Couldn't solve even 1 ques. :(
•  » » » » 3 years ago, # ^ |   +1 If you want easier problems to try on, i personally think the first few problems on AtCoder Beginner Contests are quite suitable. Have fun!
•  » » 3 years ago, # ^ |   +4 Yes, AB should be easy enough. Go do it!
 » 3 years ago, # |   +194 10 minutes delay, sorry. I'm trying to fix Ruby installation.
•  » » 3 years ago, # ^ |   +31 No problem sir. Codeforces is such a good platform that these types of delays doesn't hurt if contest go on smoothly
•  » » 3 years ago, # ^ |   +9 Contest smoothness >>>>> 10-15 minutes delay
 » 3 years ago, # |   +94 My adrenalin just got wasted
 » 3 years ago, # |   +3 Delayed by 10 minutes :/
 » 3 years ago, # |   -264 What the fuck? Why is CF so bad in punctuality? -_-
•  » » 3 years ago, # ^ |   +31 you should write the words carefully.They are doing hardwork for us
•  » » » 3 years ago, # ^ |   -52 Agreed but they can't just play with our time? Can they? :)
•  » » » » 3 years ago, # ^ |   -17 They don't force you to play this.. are they ?
•  » » » » » 3 years ago, # ^ |   -42 Did someone force you to comment here? XDNo hard feelings brother!
•  » » » » » » 3 years ago, # ^ |   -7 Did someone force you to reply here?
•  » » » » » » » 3 years ago, # ^ |   +1 Did someone force you to make an entry? :3
•  » » » » 3 years ago, # ^ |   -6 Try to compete in virtual contest then.
•  » » » » 3 years ago, # ^ |   +3 Did codeforces questioned you ever ? or did they ever ask you to pay for such an amazing platform? Be patient.
•  » » » » » 3 years ago, # ^ |   +7 Tell me the day you need to pay to codechef or topcoder or any other site that exists!
•  » » » » » » 3 years ago, # ^ |   0 True, but be patient at the same time.
•  » » » » » » » 3 years ago, # ^ |   +6 Yeah bro absolutely! All the best to you for the round! Have a large delta!
•  » » » » » » 3 years ago, # ^ |   0 Someone is talking about codechef , LOL. Can you please deactivate your codeforces account? And enjoy codechef. All the best :)
•  » » » » » » » 3 years ago, # ^ |   +3 Can we deactivate it ? :/
•  » » » » » » 3 years ago, # ^ |   0 Do we need to state the difference in the quality of Codeforces and Codechef?
•  » » 3 years ago, # ^ |   +13 A delay of 10 minutes is much better than an unrated contest or queueforces!
•  » » 3 years ago, # ^ |   +6 Calm Down,man. We all are human, we all make mistakes.
•  » » 3 years ago, # ^ |   0 Don't thank MikeMirzayanov if you can't, But please don't hurt the sentiments of the fellow codeforces users.
 » 3 years ago, # |   +28 Oh shit! Now I'll have to listen to Twice once again.
•  » » 3 years ago, # ^ |   0 Oh shit! You had to listen Twice twice, it's two squared)
•  » » » 3 years ago, # ^ |   +3 That's the number of problems I wanna solve today.
 » 3 years ago, # |   -22 This ten minute extension is ruining the moment :(
 » 3 years ago, # |   -20 my precious time....22:35->22:45
•  » » 3 years ago, # ^ |   +35 Just solve all the problems 10m faster :)
 » 3 years ago, # |   0 Delayed??
•  » » 3 years ago, # ^ |   -7 RIP all my excitement.
 » 3 years ago, # |   -8 Is today's contest suitable for newbie and lower pupil?
•  » » 3 years ago, # ^ |   -8 Yes...I think by solve a,b we can increase our rating easily !!
•  » » 3 years ago, # ^ |   +1 A and B should be solvable by everyone, I think. But even if they weren't, participating in a contest is always suitable.
•  » » » 3 years ago, # ^ |   0 Hope I can make A and B
•  » » 3 years ago, # ^ |   0 Even if you couldn't solve any problem during the contest, you will learn something from the editorial afterward.
 » 3 years ago, # |   -49 What the fuck! Another 10 minute wasted. 10 min wasted before starting by waiting.
•  » » 3 years ago, # ^ |   +15 Codeforces is doing hardwork for free. You should not say these 10min wasted. Its way much better than an unrated contest due to long queues.
•  » » » 3 years ago, # ^ |   +10 sorry bro
 » 3 years ago, # |   -16 Ok, all set, 5.4.3.2.1 let's start..........not now, come again after 10 min xd
 » 3 years ago, # | ← Rev. 2 →   -16 [deleted]
 » 3 years ago, # |   +52 An interesting observation: all the people complaining about adrenaline being washed out etc. are below blue and below.
•  » » 3 years ago, # ^ |   +31 Interesting observation: all the people always having problem about something and not taking a joke as a joke are purple and above
 » 3 years ago, # |   +3 Codeforces Global Round Exists:
 » 3 years ago, # |   +20 As a contestant, I just read the questions
 » 3 years ago, # |   +12 This was the Hardest A i have seen till now.
•  » » 3 years ago, # ^ |   0 Not at all :| Hard but not hardest !!
•  » » » 3 years ago, # ^ |   0 How can you tell me on my behalf.i said i have seen till now,read the comment again.
•  » » » » 3 years ago, # ^ |   0 Cause you attend 62 more contest..it is not so hard.
•  » » » » » 3 years ago, # ^ |   0 I think i got horrified from the contest announcement.XD
•  » » 3 years ago, # ^ |   +4 For me A was harder than B and C. Took me a while to reach the solution
•  » » » 3 years ago, # ^ |   0 Same here solved A in total 1:30 hrs and C in 10 minutes. xD
•  » » » » 3 years ago, # ^ |   0 But C's logic was beautiful though, i was scared that am i missing some case here.
 » 3 years ago, # |   +12 As a tester, I am very happy that I can enjoy others suffering in the contest. This line become true lol. But really awesome problemset
 » 3 years ago, # |   +58 i should have taken those feedbacks seriously :(
•  » » 3 years ago, # ^ |   +4 Your graph is really inspiring
•  » » » 3 years ago, # ^ |   +3 No, it's not rather it shows how dumb i'm :(
 » 3 years ago, # |   0 Very good contest nice problemset
 » 3 years ago, # |   -7 hope mifafaovo gets dethroned by umnik this time!
 » 3 years ago, # |   0 [*] rating
 » 3 years ago, # |   +138 As a participant, this round gave me PTSD. XD
•  » » 3 years ago, # ^ |   0 I gave this contest in the hope for specialist but it seems that still specialist is far away from me... BTW logic for 3rd one is "NO" if(a[0] > a[n-1] ) , else "YES"
•  » » » 3 years ago, # ^ |   0 Permutation Forces...
•  » » 3 years ago, # ^ |   +25 I think I need more IQ to solve problem like these, not algorithm knowledge. :)
 » 3 years ago, # |   0 Arggg. Tough round. Great problems, though!
 » 3 years ago, # |   +161 Ari: how many constructive problems do we need?Other setters: Yes
 » 3 years ago, # |   +1 Great round with difficult problems. Hoping for a fast editorial.
 » 3 years ago, # |   +241
•  » » 3 years ago, # ^ |   0 Your memes are so good always bro !!
 » 3 years ago, # |   +11 I wonder who did created problem D.
•  » » 3 years ago, # ^ |   +7 how to solved D ?
 » 3 years ago, # | ← Rev. 2 →   +185 Never again.
•  » » 3 years ago, # ^ |   0 Thus, hocky went and made a catfish farm instead. He is now known as the catfish farmer.
 » 3 years ago, # |   +8 Is there anyone else who could solve D in like 10-15 minutes and has no idea about solving C? Bad day!Anyways how to solve C?
•  » » 3 years ago, # ^ |   +8 The last element must be greater than the first
•  » » 3 years ago, # ^ |   0 how to solved D ?
•  » » 3 years ago, # ^ |   +3 arr[0] < arr[n-1] => YES else NO
•  » » 3 years ago, # ^ |   0 if(a[n-1]>a[0]) cout<<"YES\n"; else cout<<"NO\n";
•  » » 3 years ago, # ^ | ← Rev. 3 →   +4 if $a[0] < a[n - 1]$ then "YES" else "NO"Consider this example5 6 7 4 8 9 10 13 11 12This can be visiualize as $[increasing] [increasing] [increasing]$5 6 7 4 8 9 10 13 11 12 But How we are breaking this sequence ?We are considering $first$ and $last$ will remain in the end of the process. So our focus is to remove all the element in between.See, 4 $<$ 5 $(first element)$, this will insert break in our sequence, from this index we will start making new increasing sequence.Similarly observe, 13 < 12 $(last element)$, this will insert a breaking point.Now, if you think a little about it, you will see we can merging first increasing sequence and last increasing sequence like this5 6 7 4 8 9 10 13 11 12 ==> 5 6 7 4 11 12 ==> 5 6 7 11 12So the sufficient condition would be $a[0] < a[n - 1]$ for answer to be exists.
•  » » 3 years ago, # ^ | ← Rev. 3 →   +5 34 people (and 2 in under the next such question) have replied to this comment but no one has even slightly explained why this is true. What's the use of such responses?
•  » » » 3 years ago, # ^ |   +52 Many of them don't know. :p
•  » » » 3 years ago, # ^ | ← Rev. 2 →   0 I proved it first before solving it. PLease Correct me If I go wrong any where. Let me explain the proof very clearly. if the minimum element of permutation that is '1' is last element of the array then plainly answer is No because no matter which ever operation you performed.the last 2 elements after operation will have minimum element that is '1' on RHS which means it is not possible to satisfy the condition that is a[i] b we cannot.
•  » » 3 years ago, # ^ |   +3 Observation 1: you can't make any operation that decreases the 1st element Observation 2: you can't make any operation that increases the last element If the 1st element is greater than the last elements, then in the best case you'll end up with 2 elements [a1 a2] where a1 > a2. Otherwise there is an easy method to eliminate all but 1 element.
•  » » 3 years ago, # ^ |   0 You have to remove the greater element in permutation while you can. If this element become the last in sequence, print YES, if you cannot remove the greater element, print NO. This is the key idea
 » 3 years ago, # |   0 Can someone tell how to solve problem C?
•  » » 3 years ago, # ^ |   0 If v[1] > v[n] print "NO"
•  » » 3 years ago, # ^ |   0 Check if the first element is smaller than the last element
 » 3 years ago, # | ← Rev. 3 →   +107 Problem setters and testers to all the participants rn:
 » 3 years ago, # | ← Rev. 4 →   +21 G is a good problem for Div2D?I guess a subsegment of the problems is reversed before the contest...
 » 3 years ago, # |   0 You will be given 2 hours and 30 minutes to solve 9 problems, and we highly encourage you to read all of them :)Did they want us to suffer? There is no gap only between A and B, E and F
 » 3 years ago, # |   0 I really need to start thinking in multiple directions before coding. Had I done that I could have solved A much much earlier :(Leason learnt.
 » 3 years ago, # |   +20 Probably should've listened to the Round Feedback.
 » 3 years ago, # |   +18 I am pretty much impressed that a trivial thing can be stated in such a difficult way (problem E).
•  » » 3 years ago, # ^ |   0 I haven't done anything trivial in E.
•  » » » 3 years ago, # ^ |   +8 E is just a bubble sort problem, written in a non-obvious way.
•  » » » » 3 years ago, # ^ |   +18 I am shocked.
•  » » 3 years ago, # ^ |   +11 Imo the thing not THAT trivial either
•  » » » 3 years ago, # ^ |   0 I'm not saying solving this problem is trivial, of course. I can accept the opinion that the bubble sort might be non-trivial.
 » 3 years ago, # |   +91 Why did you put the easiest problem as G?
•  » » 3 years ago, # ^ |   +28 +1, that was some kind of a joke xd
 » 3 years ago, # |   +9 E killed my will to live, how to solve that?
•  » » 3 years ago, # ^ |   +22 Transform the array into a permutation by considering pairs ($a_i,i$). Use bubble sort on the inverse of that permutation; each swap of elements which differ by 1 only remove that inversion.
•  » » 3 years ago, # ^ |   +35 In a non-sorted permutation there is always a pair of consecutive numbers which are in wrong order. You can swap them and it doesn't affect any other inversion.
•  » » » 3 years ago, # ^ |   0 I tried to implement this for like an hour or more :/ Need to study the solutions.
•  » » » » 3 years ago, # ^ |   0 Hi, I'm still a little confused with the statement that "it doesn't affect any other inversion".In eg: 3 1 2, when we swap (3,2) we get 2 1 3, but here we created a new inversion (2,1).Can someone explain this please? Thanks.
•  » » » » » 3 years ago, # ^ |   0 With 3 1 2 there are two inversions. Positions (1,2) and (1,3). We swap (1,3) because of the min diff of those two inversions. Then we swap the other inversion (position 1 and 2) resulting in 1 2 3.
•  » » » » » » 3 years ago, # ^ |   0 Why can't we perform swap of positions (1,2) and then (2,3). The value array will transform as follows : 3 1 2 -> 1 3 2 -> 1 2 3
•  » » » » » » » 3 years ago, # ^ | ← Rev. 2 →   +1 No. 3 1 2 swap positions (1,2) -> 1 3 2 swap positions (1,3) -> 2 3 1Note that we do not swap "the positions of..." or something like this. We swap the positions as given in the inversions.
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