### ssense's blog

By ssense, history, 5 months ago,

## Hello Codeforces!

I_Love_YrNameCouldBeHere and I are glad to invite you to Unofficial Div 4 Round #2. Which will take place this Wednesday at 14:35 UTC (The round is over now, but you can still participate virtually). The round will not be rated for any participants since it is unofficial.

You will be given six tasks and two hours to solve them. The problems were created and prepared by ssense and I_Love_YrNameCouldBeHere for users with a rating range from 0 to 1400 but anyone is welcome to participate in the round!

We want to thank everyone who was involved in the round preparation:

Errichto for thorough testing and publishing this round on the gym.

Also, after the contest Errichto will post videos about this contest and the responsibilities of a tester.

UPD: Videos are now up: Fixing A, Testing A, Testing the rest.

Brodicico for help with problems and testing the round.

And a huge thank you to the testers: Errichto, 1-gon, galen_colin, gupta_samarth, arujbansal, Chihai_Ion and Grumpah .

MikeMirzayanov for Polygon and Codeforces platforms.

Even though the contest is unrated, we believe it is an excellent way of practice, especially for Div 4 users.

Remember, if you don't know how to solve one problem, look at others!

UPD 1: Registration available now!

UPD 2: Round is over! We hope you enjoyed the problems and congratulations to the winners!

UPD 3: Editorial is out!

Div. 4 winners:

Not Div.4 Winners:

First to solve each problem:

A: First: Valera_Grinenko

Div. 4 first: anuragdvd

B: First: Geothermal

Div. 4 first: Lelouch_1

C: First: Geothermal

Div. 4 first: Lelouch_1

D: First: Geothermal

Div. 4 first: RamPrabodhInduri

E: First: Geothermal

Div. 4 first: -deleted-

F: First: IgorI

Div. 4 first: sahaun

• +244

 » 5 months ago, # |   +167 As a tester, the setters are holding me hostage and forcing me to make an "as a tester" comment.
•  » » 5 months ago, # ^ |   +73 As a setter you have fulfilled your goal, you're no longer needed.
•  » » » 5 months ago, # ^ |   +61 As a father, you guys will regret forcing my son to use his super powers
•  » » » » 5 months ago, # ^ |   +28 We didn't force him, we asked him nicely :)
•  » » 5 months ago, # ^ |   -20 Stop lying. They already have sir digon's permission.
 » 5 months ago, # |   +76 as a fellow tester, .... You know the drill
 » 5 months ago, # |   +25 As not a tester, the setters are not holding me hostage and forcing me to make an "as a not tester" comment. Good luck to all participating. May your cp girlfriends help you solve all the problems.
 » 5 months ago, # |   +167 I recorded the process of testing this round and complaining about bad statements, weak tests, etc. I even told the authors to replace one problem because it was stupid. That was a few weeks ago and the contest is well-prepared now, so I recommend participating.On a related note, I'm going to create a guide on how to properly test a problem, especially in Polygon. Implementing a correct solution is actually less important than checking the validator, going through sample test explanation, or stress-testing the main solution with brute force. We get so many testers in CF rounds nowadays but they usually just solve problems. That being said, testing by solving problems still helps a lot in many aspects like estimating the difficulty and choosing proper TL, so it's great that testers are so appreciated recently!
•  » » 5 months ago, # ^ |   +39 Sounds like a lecture I need to pay attention to XD. Thanks for all the work, I know from experience that testing a full round is a big time and effort commitment
•  » » » 5 months ago, # ^ |   +38 Indeed, it takes a lot of time to plan the dumbest comment that maximizes contribution.
 » 5 months ago, # |   +43 As the only cyan tester...
 » 5 months ago, # |   +6 I would like to thank ssense, SlavicG, Errichto, AlexNeagu, Monogon, galen_colin, gupta_samarth, arujbansal, Chihai_Ion, Grumpah, MikeMyrzayanov for being orz.Also for creating a div 4 round! I hope noob like me can win it!
 » 5 months ago, # |   +3 ssense I_Love_YrNameCouldBeHere i think your Div.4 idea is very good. Wish we had regular Div.4 in Codeforces. It's very good practive for newbies like me (only 141 points at IATI Shumen Junior).
•  » » 5 months ago, # ^ |   +13 oi!
 » 5 months ago, # |   +6 It's a great idea to have these rounds. Hope to see more like this in the future.
 » 5 months ago, # |   +3 What is the range difficulty of rating of problems?
•  » » 5 months ago, # ^ |   0 <=1400
 » 5 months ago, # |   +3 thank you so much for all who help to create this round for us.
 » 5 months ago, # |   +2 That would be great for beginners :) Hope to see more like this in the future
 » 5 months ago, # |   +3 RZK_19 see this
 » 5 months ago, # |   0 thank you.
 » 5 months ago, # |   0 How to win this? Strategy is required !
•  » » 5 months ago, # ^ |   +10 Solve Problems
 » 5 months ago, # |   +27 ping, it starts in 5 minutes.
 » 5 months ago, # |   0 very long queue now , i m exiting from the contest . Sorry guys i hope it will be better next time
•  » » 5 months ago, # ^ |   +6 Div4 round too powerfulThe queue wasn't too bad. For me it was just a few minutes, which isn't ideal but it's workable.
•  » » 5 months ago, # ^ |   0 Why exit, try the next one
•  » » » 5 months ago, # ^ |   0 Yeah guys after eating the dinner i did participated again and i solved 5 except E which i solved in no time after the contest . Good round . I am not a judge so an opinion is that it should have problems of little bit more difficulty like 200 ratings higher maybe 1600++ .
•  » » » » 5 months ago, # ^ |   +4 So you want a div 3 round?
 » 5 months ago, # |   +3 Nice set of problems!
•  » » 5 months ago, # ^ |   -9 nah
 » 5 months ago, # |   +3 Is it Div. 5?
•  » » 5 months ago, # ^ |   +8 It looks like div.5, but problems were good.
 » 5 months ago, # |   0 Problems were interesting with respect to div 4 :D Had fun! Thank You for this round.
•  » » 5 months ago, # ^ |   0 Glad you had fun!
 » 5 months ago, # |   +1 can anyone plz explain approach to f
•  » » 5 months ago, # ^ |   0 Editorial is coming!
•  » » » 5 months ago, # ^ |   0 Actually,cant wait.well thank u .enjoyed the problemset.would love to have such contests more frequently.
•  » » » » 5 months ago, # ^ |   0 Editorial is out!
•  » » 5 months ago, # ^ |   +1 HintTry for $\text{n mod 4 = 0}$.
•  » » » 5 months ago, # ^ |   0 well i have predicted a draw if(n%4==0); else if(n&1) bob wins; else alice wins;
•  » » » » 5 months ago, # ^ |   0 I saw your code. Your logic is ok. But you missed the newline after Draw and Alice.
•  » » » » » 5 months ago, # ^ |   0 ok.thanks
 » 5 months ago, # | ← Rev. 3 →   +23 Sorry about the long queue. Something was wrong with the system at the beginning and nothing was being judged. When everything started working properly after half an hour or so, the waiting time was at some peaks around 5 minutes and that was my bad because we had a lot of tests. I should have predicted that there will be enough participants that testing time might be an issue. Sorry! But again, the first 30 minutes were about unlucky technical issues :(It was extra annoying that there was some CF error and we couldn't make any public announcement. We wanted to at least say something like "We're sorry about a long queue, it should be fixed soon".
 » 5 months ago, # | ← Rev. 2 →   +27 Here's a 1-hour recording of me fixing a badly prepared problem A, and explaining to authors what should be done better. Half of the video is about generating good tests so maybe it's more useful for problem setters rather than for testers. https://youtu.be/KnMOEiySz0YUPDInitial testing of A: https://youtu.be/L6cb9IOv4cETesting of the whole round: https://youtu.be/I7AJtUcVoxwComing later: a guide for testers.
•  » » 5 months ago, # ^ |   +8 Hey, thank you for making this. This is a really nice resource for anyone who wants to set problems.This should get more love. Can you post this as a separate blog?
•  » » » 5 months ago, # ^ |   +5 I will spend some more time on this to create a list of tips, and then post it on CF as a blog.
 » 5 months ago, # |   +18 In E statement said contain string t. It's not clear that as substring or subsequence and all the example work with two cases.
•  » » 5 months ago, # ^ |   +10 Sorry for the confusion.
•  » » 5 months ago, # ^ |   +3 I was trying to solve the subsequence problem all the time :( and that solution actually passed 14 test cases which made my belief even stronger
 » 5 months ago, # |   0 The problems were good. Kudos to everyone for organizing this round. It will be good to have rounds like these in the future.
 » 5 months ago, # |   +27 First time I am mentioned as a "winner" in a blog post, hopefully not the last one :D