### Vovuh's blog

By Vovuh, history, 21 hour(s) ago, ,

Hi everyone! I'm glad to invite all of you to participate in Codeforces Round #574 (Div. 2) which will take a place in Jul/17/2019 17:35 (Moscow time).

This round is based on SIS team contest. You will be given 6 problems and 2 hours to solve them. This round will be rated for Div. 2 participants. In other words, this round will be rated for the participants with rating lower than 2100. As usual, participants from the first division are welcome to join out of competition.

Problems was invented and prepared by Nebuchadnezzar, Kurpilyansky, meshanya, TsarN, sava-cska, ima_ima_go and senek_k. I am just a coordinator of this round, I made a small amount of work such as English translations and editorials. I want to thank Mikhail MikeMirzayanov Mirzayanov for amazing systems Codeforces and Polygon, all authors of this great contest, KAN and _kun_ for help with difficulties estimating and choosing the problems and my dear friend Ivan BledDest Androsov for help with round preparation!

Good luck everyone and see only green system testing messages! :)

• +143

By Vovuh, history, 3 weeks ago, ,

1183A - Nearest Interesting Number

Idea: MikeMirzayanov

Tutorial
Solution

1183B - Equalize Prices

Idea: MikeMirzayanov

Tutorial
Solution

1183C - Computer Game

Idea: MikeMirzayanov and Vovuh and BledDest

Tutorial
Solution

1183D - Candy Box (easy version)

Idea: MikeMirzayanov

Tutorial
Solution

1183E - Subsequences (easy version)

Idea: MikeMirzayanov

Tutorial
Solution

1183F - Topforces Strikes Back

Idea: Vovuh

Tutorial
Solution

1183G - Candy Box (hard version)

Idea: MikeMirzayanov

Tutorial
Solution

1183H - Subsequences (hard version)

Idea: MikeMirzayanov

Tutorial
Solution

• +64

By Vovuh, history, 3 weeks ago, ,

<almost-copy-pasted-part>

Hello! Codeforces Round #570 (Div. 3) will start at Jun/26/2019 17:35 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</almost-copy-pasted-part>

UPD: I also would like to thank Ashishgup and kocko for help with round preparation and testing!

UPD2: The contest will be extended for 15 minutes because the problems are more interesting than we thought. We also advise to read all the problems because some of them may have the same difficulty and we cannot know which one will be easier for you than the other.

UPD3: Editorial is published!

UPD4:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 MbahFaishol1937 8 248
2 bertmin 8 450
3 BaiBatyr 8 455
4 LJF007 7 305
5 proizvedenie 7 322

Congratulations to the best hackers:

Rank Competitor Hack Count
1 Nazarbek_Baltabaev 120:-90
3 yzm10 36:-2
4 csegura 31
5 shaker007 30:-11
798 successful hacks and 492 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A blast 0:01
B Kirill_Kudr22 0:04
C I_love_HellHoleStudios 0:04
D divya_rawat 0:10
E llbra9z 0:13
F FlyInTheSky 0:42
G MbahFaishol1937 0:27
H UMP45 0:25

• +177

By Vovuh, history, 5 weeks ago, ,

1176A - Divide it!

Idea: Vovuh

Tutorial
Solution

1176B - Merge it!

Idea: MikeMirzayanov

Tutorial
Solution

1176C - Lose it!

Idea: Vovuh

Tutorial
Solution

1176D - Recover it!

Idea: MikeMirzayanov

Tutorial
Solution

1176E - Cover it!

Idea: MikeMirzayanov

Tutorial
Solution

1176F - Destroy it!

Idea: BledDest

Tutorial
Solution

• +46

By Vovuh, history, 6 weeks ago, translation, ,

<almost-copy-pasted-part>

Hello! Codeforces Round #565 (Div. 3) will start at Jun/09/2019 17:35 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</almost-copy-pasted-part>

UPD1: Big thanks to Um_nik, Rudy358, nigus, opukittpceno_hhr and Temotoloraia for testing the round! And also big thanks to my dear friends Ivan BledDest Androsov, Roman Roms Glazov and Mikhail PikMike Piklyaev for help with round preparation!

UPD2: Editorial is published!

UPD3:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 Yushen 6 235
2 Violet_user 6 293
3 BudiArb 6 345
4 xenoframium 6 350
5 njchung93 6 439

Congratulations to the best hackers:

Rank Competitor Hack Count
1 nikolapesic2802 69:-15
2 stefdasca 42:-11
3 dorijanlendvaj 15:-11
4 orz_liuwei 10:-11
5 interestingLSY 5:-1
170 successful hacks and 236 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A riz_1_ 0:02
B _ekaterina_dudina 0:04
C BudiArb 0:05
D hxylalala 0:18
E csts.21 0:17
F njchung93 0:32

• +146

By Vovuh, history, 7 weeks ago, ,

1170A - Three Integers Again

Idea: Vovuh

Solution: elizarov

Tutorial
Solution

Idea: MikeMirzayanov

Solution: elizarov

Tutorial
Solution

1170C - Minus and Minus Give Plus

Idea: MikeMirzayanov

Solution: elizarov

Tutorial
Solution

1170D - Decoding of Integer Sequences

Idea: MikeMirzayanov

Solution: elizarov

Tutorial
Solution

1170E - Sliding Doors

Solution: elizarov

Tutorial
Solution

1170F - Wheels

Idea: MikeMirzayanov, Vovuh, pashka

Solution: Benq

Tutorial
Solution

1170G - Graph Decomposition

Idea: MikeMirzayanov

Solution: elizarov

Tutorial
Solution

1170H - Longest Saw

Idea: MikeMirzayanov

Solution: pashka

Tutorial
Solution

1170I - Good Subsets

Idea: MikeMirzayanov

Solution: pashka

Tutorial
Solution

Tutorial of Kotlin Heroes

• +47

By Vovuh, history, 2 months ago, ,

1165A - Remainder

Idea: Vovuh

Tutorial
Solution

1165B - Polycarp Training

Idea: MikeMirzayanov

Tutorial
Solution

1165C - Good String

Idea: BledDest

Tutorial
Solution

1165D - Almost All Divisors

Idea: MikeMirzayanov

Tutorial
Solution

1165E - Two Arrays and Sum of Functions

Idea: Vovuh

Tutorial
Solution

1165F1 - Microtransactions (easy version)

Idea: BledDest

Tutorial
Solution

1165F2 - Microtransactions (hard version)

Idea: BledDest

Tutorial
Solution

• +32

By Vovuh, history, 2 months ago, ,

I have nothing to say this time, so meet yet another Div. 3 round :)

<almost-copy-pasted-part>

Hello! Codeforces Round #560 (Div. 3) will start at May/14/2019 17:35 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</almost-copy-pasted-part>

UPD: I also would like to thank nhho, chenjb and ksun48 for testing the round.

UPD2: I also would like to thank my friend Adilbek adedalic Dalabaev for valuable suggestions about the contest and testing it!

UPD3: Editorial is published!

UPD4:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 nuoyanli 7 368
2 Vaseline_Warrior 7 437
4 1716638489 7 604
5 leo990629 6 335

Congratulations to the best hackers:

Rank Competitor Hack Count
1 Java 68:-2
2 figdan 63:-13
3 makjn10 44:-1
4 csts.21 40
5 yashi2552 27
872 successful hacks and 341 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A Tokisaki-Kurumi 0:03
B CoolAttacks 0:03
C igniubi 0:08
D foool 0:13
E maverick_10 0:15
F1 cunt 0:27
F2 cunt 0:26

• +118

By Vovuh, history, 3 months ago, ,

1157A - Reachable Numbers

Idea: BledDest

Tutorial
Solution

1157B - Long Number

Idea: BledDest

Tutorial
Solution

1157C1 - Increasing Subsequence (easy version)

Idea: MikeMirzayanov

Tutorial
Solution

1157C2 - Increasing Subsequence (hard version)

Idea: MikeMirzayanov

Tutorial
Solution

1157D - N Problems During K Days

Idea: MikeMirzayanov

Tutorial
Solution

1157E - Minimum Array

Idea: Vovuh

Tutorial
Solution

1157F - Maximum Balanced Circle

Idea: MikeMirzayanov

Tutorial
Solution

1157G - Inverse of Rows and Columns

Idea: Vovuh

This is the comment about the quadratic solution. Thank you so much for mentioning this fact, STommydx!

Tutorial
Solution

• +34

By Vovuh, history, 3 months ago, translation, ,

Suddenly, this round will consist of 7 different problems also!

UPD2: The round will consist of 7 problems and one of them will be in easy and hard editions!

<almost-copy-pasted-part>

Hello! Codeforces Round #555 (Div. 3) will start at Apr/26/2019 17:35 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</almost-copy-pasted-part>

UPD0: I also would like to thank my friend Adilbek adedalic Dalabaev for helping me with understanding problems difficulty and other help with round preparation!

UPD1: Big thanks to dreamoon_love_AA, Ashishgup, jeel_vaishnav and lizi_lzy for testing the round!

UPD3: Editorial is published!

UPD4:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 FloodBenz 8 282
2 maguihong123 7 347
3 dreagonm 7 373
4 DeathYmz 7 571
5 BaiBatyr 6 189

Congratulations to the best hackers:

Rank Competitor Hack Count
1 WileE.Coyote 448:-33
2 Disappointment 127:-20
3 wzw19991105 39
4 ismagilov.code 50:-23
5 Kucha 20:-3
919 successful hacks and 365 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A ImAlsoChildish 0:01
B BaiBatyr 0:06
C1 darshit_99 0:10
C2 Injetzk 0:16
D iamnotacoder 0:21
E BaiBatyr 0:12
F Injetzk 0:29
G Injetzk 1:15

• +176

By Vovuh, history, 3 months ago, ,

1154A - Restoring Three Numbers

Idea: MikeMirzayanov

Tutorial
Solution

1154B - Make Them Equal

Idea: MikeMirzayanov

Tutorial
Solution

1154C - Gourmet Cat

Idea: le.mur

Tutorial
Solution

1154D - Walking Robot

Idea: MikeMirzayanov

Tutorial
Solution

1154E - Two Teams

Idea: MikeMirzayanov

Tutorial
Solution

1154F - Shovels Shop

Idea: MikeMirzayanov

Tutorial
Solution

1154G - Minimum Possible LCM

Idea: MikeMirzayanov

Tutorial
Solution

• +38

By Vovuh, history, 3 months ago, translation, ,

This time I have nothing to say except that this round will consist of 7 different problems!

<almost-copy-pasted-part>

Hello! Codeforces Round #552 (Div. 3) will start at Apr/16/2019 17:35 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</almost-copy-pasted-part>

UPD: Thanks to le.mur for idea of one of the problems.

UPD2: Editorial is published now!

UPD3:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 ysluo2000 7 229
2 fake_delete_pls2 7 251
3 KefaKuma 6 178
4 Zhao-L 6 222
5 haimiaoyuzhao 6 240

Congratulations to the best hackers:

Rank Competitor Hack Count
1 wzw19991105 49:-4
2 ScreaMood 42:-1
3 I_love_Maria_Krylova 35:-5
4 Hacked_ 31:-1
5 Zombie358 30:-7
949 successful hacks and 502 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A MinatoYukina 0:01
B MinatoYukina 0:04
C Chess_fan 0:08
D nikizakr 0:07
E FluffyTT 0:21
F FluffyTT 0:09
G 1tst 0:14

• +200

By Vovuh, history, 4 months ago, ,

1144A - Diverse Strings

Idea: MikeMirzayanov

Tutorial
Solution

1144B - Parity Alternated Deletions

Idea: MikeMirzayanov

Tutorial
Solution

1144C - Two Shuffled Sequences

Idea: MikeMirzayanov

Tutorial
Solution

1144D - Equalize Them All

Idea: Vovuh

Tutorial
Solution

1144E - Median String

Idea: Vovuh

Tutorial
Solution

1144F - Graph Without Long Directed Paths

Idea: MikeMirzayanov

Tutorial
Solution

1144G - Two Merged Sequences

There is different solution for the problem, it is pretty interesting! Thanks, Roundgod!

Idea: Vovuh

Tutorial
Solution

• +47

By Vovuh, 4 months ago, translation, ,

Hello! Hope you missed me :) As far as some people say, because of copy-pasted announcement this round wouldn't be interesting. But the real thing is that I'm very sick now and I'm very glad that I prepared this round at all. Hope you will enjoy it. Good luck to all!

<copy-pasted-part>

Hello! Codeforces Round #550 (Div. 3) will start at Mar/31/2019 17:05 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</copy-pasted-part>

UPD: Editorial is published!

UPD2:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 WNSGB 7 206
2 kaixinqi 7 335
3 _sysjuruo 6 188
4 Moririn2528 6 206
5 CarusoX 6 212

Congratulations to the best hackers:

Rank Competitor Hack Count
1 wanderer163 21
2 tokitsukaze 14
3 nazarov.shohrukh 6
4 SMit_mangukiya 4
5 VikasChandak 4
93 successful hacks and 132 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A anurag918273 0:02
B probIem-solving 0:07
C ProPan_without_Pro 0:05
D vnquynh_hac_am 0:12
E probIem-solving 0:28
F sjcakioi 0:16
G izone 0:20

• +168

By Vovuh, history, 4 months ago, ,

1133A - Middle of the Contest

Idea: MikeMirzayanov

Tutorial
Solution

1133B - Preparation for International Women's Day

Idea: MikeMirzayanov

Tutorial
Solution

1133C - Balanced Team

Idea: MikeMirzayanov

Tutorial
Solution

1133D - Zero Quantity Maximization

Idea: BledDest

Tutorial
Solution

1133E - K Balanced Teams

Idea: MikeMirzayanov

Tutorial
Solution

1133F1 - Spanning Tree with Maximum Degree

Idea: MikeMirzayanov

Tutorial
Solution

1133F2 - Spanning Tree with One Fixed Degree

Idea: MikeMirzayanov

Tutorial
Solution

• +33

By Vovuh, history, 4 months ago, ,

<copy-pasted-part>

Hello! Codeforces Round #544 (Div. 3) will start at Mar/07/2019 18:05 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</copy-pasted-part>

UPD0: I also would like to thank Stresshoover, dreamoon_love_AA, Nebuchadnezzar and nhho for help in testing the round!

UPD1: Editorial is published!

UPD2:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 MoNsTeR_CuBe 7 340
2 try_agian 7 370
3 HurmousDay 7 396
4 AyaOtonashi 7 404
5 N_o_o_B 7 437

Congratulations to the best hackers:

Rank Competitor Hack Count
1 greencis 72:-31
2 jhonber 30:-1
3 Milkdrop 22:-15
4 awasd 16:-3
5 MarcosK 12:-5
269 successful hacks and 316 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A friendly_potato 0:02
B OFAKMKOFZ 0:04
C MbahFaishol1937 0:03
D AyaOtonashi 0:08
E nvwa 0:22
F1 elevendigit 0:15
F2 XXMihaiXX969 0:21

• +150

By Vovuh, history, 5 months ago, ,

Idea: MikeMirzayanov

Tutorial
Solution

1118B - Tanya and Candies

Idea: MikeMirzayanov

Tutorial
Solution

1118C - Palindromic Matrix

Idea: MikeMirzayanov

I should mention this blog because it is amazing! This is a tutorial of this problem from MikeMirzayanov.

Tutorial
Solution

1118D1 - Coffee and Coursework (Easy version)

Idea: MikeMirzayanov

Tutorial
Solution

1118D2 - Coffee and Coursework (Hard Version)

Idea: MikeMirzayanov

Tutorial
Solution

1118E - Yet Another Ball Problem

Idea: MikeMirzayanov

Tutorial
Solution

1118F1 - Tree Cutting (Easy Version)

Idea: MikeMirzayanov

Tutorial
Solution

1118F2 - Tree Cutting (Hard Version)

Idea: MikeMirzayanov

Tutorial
Solution

• +62

By Vovuh, history, 5 months ago, translation, ,

Miss Div. 3 rounds? :)

<copy-pasted-part>

Hello!

Codeforces Round #540 (Div. 3) will start at Feb/19/2019 17:35 (Moscow time). You will be offered 6 or 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</copy-pasted-part>

UPD0: I also would like to thank zimpha and arpa for help with the round testing and finding some bugs!

UPD: Due to the problems being really interesting the round will last 2 hours 15 minutes.

UPD2:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 Ghajini 7 259
2 ACtest 7 271
3 akali 7 274
4 AuSquare 7 341
5 bonchinche 7 343

Congratulations to the best hackers:

Rank Competitor Hack Count
1 hytzongxuan 73:-9
2 MarcosK 59:-6
3 theroot 28:-1
4 yqdjl6 23:-6
5 2014CAIS01 24:-9
497 successful hacks and 574 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A 1021869 0:00
B 15Y 0:05
C oldpreisnerboy 0:11
D1 omeravci372742 0:17
D2 Ghajini 0:17
E __1900__ 0:12
F1 MoonLight_v0 0:10
F2 1021869 1:33

UPD3: Editorial is published!

• +180

By Vovuh, history, 6 months ago, ,

1108A - Two distinct points

Tutorial
Solution

1108B - Divisors of Two Integers

Tutorial
Solution

1108C - Nice Garland

Tutorial
Solution

1108D - Diverse Garland

Tutorial
Solution

1108E1 - Array and Segments (Easy version)

Tutorial
Solution

1108E2 - Array and Segments (Hard version)

Tutorial
Solution

1108F - MST Unification

Tutorial
Solution

• +36

By Vovuh, history, 6 months ago, translation, ,

<copy-pasted-part>

Hello!

Codeforces Round #535 (Div. 3) will start at Jan/23/2019 17:35 (Moscow time). You will be offered 6 or 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</copy-pasted-part>

UPD: I also would like to thank testers ismagilov.code, Nebuchadnezzar, Arpa, filippos, eddy1021 for the great help in round preparation!

UDP2: I don't sure about Iamoni so I included top-6 instead of top-5 in the table. And I'm also don't sure that some hackers aren't cheat so forgive me if my information is wrong.

UPD3: Editorial is published!

Congratulations to the winners:

 1 b31quocbao 7 358 2 GZY_AK_IOI 7 455 3(?) Iamoni 6 101 4(3?) pushkar12 6 216 5(4?) _DarkDawn_ 6 226 6(5?) Amooo 6 229

Congratulations to the best hackers:

Rank Competitor Hack Count
1 _bacali 181:-49
2 Chiakisa 55:-8
3 CNH_NHI 10:-1
4 CutieRabbit 9
5 CNH_NSIS 8
378 successful hacks and 348 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A spacewanker 0:01
B mpstxdy 0:03
C Iamoni 0:06
D arpit040199 0:06
E1 Iamoni 0:11
E2 TsingTaoDaTieWang 0:16
F Zhao-L 0:20

• +135

By Vovuh, history, 6 months ago, ,

1102A - Integer Sequence Dividing

Tutorial
Solution 1
Solution 2

1102B - Array K-Coloring

Tutorial
Solution

1102C - Doors Breaking and Repairing

Tutorial
Solution

1102D - Balanced Ternary String

Tutorial
Solution (Vovuh)
Solution (PikMike)

1102E - Monotonic Renumeration

Tutorial
Solution

1102F - Elongated Matrix

Tutorial
Solution 1
Solution 2

• +32

By Vovuh, history, 6 months ago, translation, ,

Happy New Year to all of you! So, meet another round from blue :)

<copy-pasted-part>

Hello!

Codeforces Round #531 (Div. 3) will start at Jan/09/2019 17:35 (Moscow time). You will be offered 6 or 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</copy-pasted-part>

UPD1:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 Jester 6 196
2 eneas 6 224
3 Nutella3000 6 267
4 pedulia 6 288
5 I_love_albeXL 6 297

Congratulations to the best hackers:

Rank Competitor Hack Count
1 ______-__________-______ 299:-99
2 im0qianqian 100:-3
3 greencis 97:-23
4 minhson 52:-2
5 MarcosK 35
1183 successful hacks and 1459 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A Isabella_Vesterbury 0:01
B ThankGodItsFriday 0:05
C Voronin_Ivan 0:05
D GiveMeAGirlFriend 0:16
E EremKa 0:21
F RedDreamer102 0:43

UPD2: Editorial is published!

UPD3: I forgot to thank eddy1021 for help with testing the round!

• +203

By Vovuh, history, 7 months ago, ,

1095A - Repeating Cipher

Tutorial
Solution

1095B - Array Stabilization

Tutorial
Solution

1095C - Powers Of Two

Tutorial
Solution

1095D - Circular Dance

Tutorial
Solution

1095E - Almost Regular Bracket Sequence

Tutorial
Solution

1095F - Make It Connected

Tutorial
Solution

• +31

By Vovuh, history, 7 months ago, translation, ,

My session is almost done and holidays are just around the corner. It means that it's time for another one contest! Happy New Year to all of you!

<copy-pasted-part>

Hello!

Codeforces Round #529 (Div. 3) will start at Dec/27/2018 17:35 (Moscow time). You will be offered 6 or 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participants of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</copy-pasted-part>

UPD: After the contest, you can discuss the problems in the community Discord server. Maybe I will take part in the discussion.

UPD2: Editorial is published!

UPD3: I forgot to thank my friend Roman Ajosteen Glazov for helping me with testing the round!

UPD4:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 sai_150050066 6 114
2 Skeercg 6 167
3 golubtsowroman 6 167
4 phungtienminh 6 170
5 forloop 6 183

Congratulations to the best hackers:

Rank Competitor Hack Count
1 MZuenni 219:-8
2 ______-__________-______ 105:-39
3 bacali 81:-66
4 Random456 15:-2

549 successful hacks and 540 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A ChiIIi 0:01
B GreacaEgalLuluOri2 0:02
C ChiIIi 0:05
D ChiIIi 0:12
E hahahahaha111 0:13
F kuchnaahopaayega 0:16

• +141

By Vovuh, history, 7 months ago, translation, ,

1092A - Uniform String

Tutorial
Solution

1092B - Teams Forming

Tutorial
Solution

1092C - Prefixes and Suffixes

Tutorial
Solution

1092D1 - Great Vova Wall (Version 1)

Tutorial
Solution 1
Solution 2

1092D2 - Great Vova Wall (Version 2)

Tutorial
Solution

1092E - Minimal Diameter Forest

Tutorial
Solution

1092F - Tree with Maximum Cost

Tutorial
Solution