vovuh's blog

By vovuh, history, 5 years ago, In English

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

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By vovuh, history, 5 years ago, translation, In English

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 awoo Piklyaev, Maksim Neon 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 Roms Glazov for helping me with testing the round!

UPD4:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 1Piece 6 114
2 blast 6 167
3 roma1n 6 167
4 TripToAzerbaijan 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 too_weak_too_slow 15:-2
5 gamezovladislav 11:-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 NTDnewbie 0:13
F kuchnaahopaayega 0:16

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By vovuh, history, 6 years ago, translation, In English

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

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By vovuh, history, 6 years ago, In English

I'm in the middle of the session but I'm still trying to prepare Div. 3 rounds.

<copy-pasted-part>

Hello!

Codeforces Round 527 (Div. 3) will start at Dec/18/2018 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 awoo Piklyaev, Maksim Neon 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 Roman Roms Glazov, Farkhod Farhod Khakimiyon and Alex hohomu Poon for help with testing the round.

UPD2:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 Doma_Umaru 6 331
2 BigDelta 5 141
3 AbduM 5 262
4 PauloMiranda98 5 266
5 Fill_in 5 276

Congratulations to the best hackers:

Rank Competitor Hack Count
1 MarcosK 84
2 hmducanh 67:-4
3 jsuyash1514 58
4 Warawreh 29
5 darkness_peach 25:-2

796 successful hacks and 2063 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A lee_chaerin 0:01
B ajarindong 0:02
C BigDelta 0:15
D1 Sad_reacts_only 0:26
D2 bigbigbigcat111 0:40
E Patunia 0:24
F Patunia 0:12

UPD3: Editorial is published!

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By vovuh, history, 6 years ago, In English

1077A - Frog Jumping

Tutorial
Solution

1077B - Disturbed People

Tutorial
Solution

1077C - Good Array

Tutorial
Solution

1077D - Cutting Out

Tutorial
Solution

1077E - Thematic Contests

Tutorial
Solution

1077F1 - Pictures with Kittens (easy version)

Tutorial
Solution

1077F2 - Pictures with Kittens (hard version)

Tutorial
Solution

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By vovuh, history, 6 years ago, translation, In English

I am so sorry about very long gaps between the contests but I really don't have enough time to prepare the problems. So...

<copy-pasted-part>

Hello!

Codeforces Round 521 (Div. 3) will start at Nov/16/2018 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 awoo Piklyaev, Maksim Neon 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 diolG 7 173
2 lyzqs 7 228
3 pvviet001 7 241
3 LVL 7 241
5 lukameladze1 7 250

Congratulations to the best hackers:

Rank Competitor Hack Count
1 awoo 153:-6
2 ______-__________-______ 186:-85
3 knowbody 128:-6
4 Laggay 113:-6
5 MarcosK 66:-6

1359 successful hacks and 755 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A Laggay 0:01
B Laggay 0:03
C ilya_kuzmin 0:05
D Laggay 0:12
E ilya_kuzmin 0:12
F1 Greninja. 0:29
F2 Radko 0:32

UPD2: Editorial is published!

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By vovuh, history, 6 years ago, translation, In English

1066A - Vova and Train

Tutorial
Solution

1066B - Heaters

Tutorial
Solution 1
Solution 2

1066C - Books Queries

Tutorial
Solution

1066D - Boxes Packing

Tutorial
Solution 1
Solution 2

1066E - Binary Numbers AND Sum

Tutorial
Solution

1066F - Yet another 2D Walking

Tutorial
Solution

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By vovuh, history, 6 years ago, translation, In English

After the long delay (disease, conference and many other things) the new Div.3 round is coming!

<copy-pasted-part>

Hello!

Codeforces Round 515 (Div. 3) will start at Oct/12/2018 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.

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By vovuh, history, 6 years ago, translation, In English

1042A - Benches

Tutorial
Solution

1042B - Vitamins

Tutorial
Solution

1042C - Array Product

Tutorial
Solution

1042D - Petya and Array

Tutorial
Solution

1042E - Vasya and Magic Matrix

Tutorial
Solution

1042F - Leaf Sets

Tutorial
Solution (O(n log n))
Solution (Small to Large, O(n log^2 n))
Solution (O(n))

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By vovuh, 6 years ago, translation, In English

Hello, Codeforces!

Codeforces Round 510 (Div. 2) will start at Sep/17/2018 11:05 (Moscow time). The round will be rated for Div. 2 contestants (participants with the rating below 2100). Div. 1 participants can take a part out of competition as usual.

The round will be rated for the Div. 2 participants (for everybody with rating less than 2100). The statements will be available in Russian and English languages.

This round is held on the tasks of the school stage All-Russian Olympiad of Informatics 2018/2019 year in city Saratov. The problems were prepared by awoo, fcspartakm, Neon, BledDest, Roms and vovuh. Great thanks to our coordinator cdkrot for the help with the round preparation! I also would like to thank our testers DavidDenisov, PrianishnikovaRina, Decibit and Vshining.

You will be given six problems and two hours to solve them. Scoring system will be announced traditionally closer to round start. :)

UPD: The scoring distribution is 500-1000-1500-2000-2250-2750.

UPD2: Editorial

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By vovuh, history, 6 years ago, In English

1029A - Many Equal Substrings

Tutorial
Solution (Vovuh, O(n^2))
Solution (Vovuh, prefix-function)

1029B - Creating the Contest

Tutorial
Solution (Vovuh)

1029C - Maximal Intersection

Tutorial
Solution (PikMike)

1029D - Concatenated Multiples

Tutorial
Solution (PikMike)

1029E - Tree with Small Distances

Tutorial
Solution (Vovuh)

1029F - Multicolored Markers

Tutorial
Solution (PikMike)

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By vovuh, history, 6 years ago, translation, In English

<copy-pasted-part>

Hello!

Codeforces Round 506 (Div. 3) will start at Aug/24/2018 17:50 (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 awoo Piklyaev, Maksim Neon 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 problem_destroyer420 5 209
2 syh0313 5 225
3 VinceJudge0 5 230
4 SaIah 5 234
5 EctoPlasma 5 241

Congratulations to the best hackers:

Rank Competitor Hack Count
1 halyavin 506:-92
2 antguz 121:-20
3 Anguei 50:-11
4 taran_1407 41:-1
5 zdw1999 41:-2
6 applese 40

1217 successful hacks and 926 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A i_f_y_m 0:03
B SaIah 0:03
C SaIah 0:13
D _kawaii_neko_ 0:17
E syh0313 0:43
F iamunstoppabIe 0:19

UPD2: Editorial is published.

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By vovuh, history, 6 years ago, translation, In English

1015A - Points in Segments

Tutorial
Solution (Vovuh, O(n + m))
Solution (Vovuh, O(n * m))

1015B - Obtaining the String

Tutorial
Solution (Vovuh)

1015C - Songs Compression

Tutorial
Solution (Vovuh)

1015D - Walking Between Houses

Tutorial
Solution (BledDest)

1015E1 - Stars Drawing (Easy Edition)

Tutorial
Solution (MikeMirzayanov, O(n^3))

1015E2 - Stars Drawing (Hard Edition)

Tutorial
Solution (Vovuh, O(n^2))

1015F - Bracket Substring

Tutorial
Solution (Vovuh)

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By vovuh, history, 6 years ago, translation, In English

<copy-pasted-part>

Hello!

Codeforces Round 501 (Div. 3) will start at Jul/31/2018 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 awoo Piklyaev, Maksim Neon Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

</copy-pasted-part>

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.

UPD1: Editorial is published.

UPD2:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 Wavyn 7 245
2 delete4 6 168
3 BernardoSulzbach 6 212
4 dongshunyao 6 214
5 jiaangk_ 6 217

Congratulations to the best hackers:

Rank Competitor Hack Count
1 halyavin 354:-66
2 test616.cpp 66:-7
3 OlaAdel 18
4 antguz 21:-7
5 wanderer163 20:-5

604 successful hacks and 446 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A 314rate 0:01
B 314rate 0:06
C garipov.roma 0:07
D shanghaiKingCsl8 0:12
E1 Ka55un0 0:30
E2 Ka55un0 0:30
F shanghaiKingCsl8 0:48

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By vovuh, history, 6 years ago, In English

1006A - Adjacent Replacements

Tutorial
Solution (Vovuh)

1006B - Polycarp's Practice

Tutorial
Solution (Vovuh)

1006C - Three Parts of the Array

Tutorial
Solution (Vovuh, set)
Solution (ivan100sic, two pointers)

1006D - Two Strings Swaps

Tutorial
Solution (Ne0n25)

1006E - Military Problem

Tutorial
Solution (mareksom)

1006F - Xor-Paths

Tutorial
Solution (Vovuh)

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By vovuh, history, 6 years ago, translation, In English

Hello!

Finally I am freed from the big part of summer cares and I can continue the preparation of Div. 3 rounds! I decided to add something written by me to this blog because TryToKnowMe (and many others, i think) noticed that i am really copy and paste this text from one announcement to another changing only contest name and start time. But... Who knows, may be this time which is saved by copy-pasting the announcement allows me to prepare the problems better?... Let it stay a mystery. So, let's go.

Codeforces Round 498 (Div. 3) will start at Jul/16/2018 17:35 (Moscow time). You will be offered 6 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 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 awoo Piklyaev, Maksim Neon Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

UPD: Also great thanks to the testers uwi, mareksom and ivan100sic for their invaluable help with the round preparation!

UPD2: Results table!

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 wendy_virgo 6 236
2 TwentyOneHundredOrBust 6 237
3 zwgtxdy 6 265
4 Syvail 6 273
5 khadgar1998 6 279

Congratulations to the best hackers:

Rank Competitor Hack Count
1 jhonber 131:-7
2 antguz 9
3 pye 9:-3
4 djm03178 6:-1
5 imlk 4

199 successful hacks and 232 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A eggmath 0:01
B eggmath 0:06
C vangtrangtan 0:07
D MoreThanANoob 0:23
E Student_of_Husayn 0:07
F NoTrolleNoLife 0:18

UPD3: Editorial is published.

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By vovuh, history, 6 years ago, In English

1003A - Polycarp's Pockets

Tutorial
Solution (Vovuh)

1003B - Binary String Constructing

Tutorial
Solution (Vovuh)

1003C - Intense Heat

Tutorial
Solution (PikMike)

1003D - Coins and Queries

Tutorial
Solution (Vovuh)

1003E - Tree Constructing

Tutorial
Solution (Vovuh)

1003F - Abbreviation

Tutorial
Solution (Vovuh)

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By vovuh, history, 6 years ago, translation, In English

Hello!

Codeforces Round 494 (Div. 3) will start on July 3 (Tuesday) at 14:35 (UTC). You will be offered 6 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 problems and 2 hours to solve them.

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 Mikhail awoo Piklyaev, Maksim Neon Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

UPD: Editorial

UPD2:

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 peanutpedo20 6 194
2 Sakurak 6 363
3 Mr.HP 6 404
4 CrownJJ 6 417
5 Skypiea 5 153

Congratulations to the best hackers:

Rank Competitor Hack Count
1 Osama_Alkhodairy 32:-3
2 Al-Merreikh 26
3 SovietPower 23:-1
4 neelbhallabos 22:-2
5 Milkdrop 20:-3

419 successful hacks and 670 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A Skypiea 0:00
B Rinne 0:08
C quality 0:10
D adamgibiadam 0:11
E peanutpedo20 0:39
F peanutpedo20 0:55

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By vovuh, history, 6 years ago, translation, In English

I'm really sorry for the issue with the problem D difficulty, it was much harder than i expected, and there was a big difficulty gap between problems C and D. I hope in the next rounds it will never happen again.

UPD: I'd like to say a big thanks to kevinsogo for the great help with tutorials and the round preparation in general.

999A - Mishka and Contest

Tutorial
Solution (Vovuh)

999B - Reversing Encryption

Tutorial
Solution (Vovuh)

999C - Alphabetic Removals

Tutorial
Solution 1 (Vovuh)
Solution 2 (Vovuh)

999D - Equalize the Remainders

Tutorial
Solution (Vovuh)

999E - Reachability from the Capital

Tutorial
Solution (Vovuh)
Linear Solution (Vovuh)

999F - Cards and Joy

Tutorial
Solution (Vovuh)

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By vovuh, history, 6 years ago, translation, In English

Hello!

Codeforces Round 490 (Div. 3) will start on June 21 (Thursday) at 14:35 (UTC). You will be offered 6 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 problems and 2 hours to solve them.

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 Mikhail awoo Piklyaev, Maksim Neon Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

UPD: Also great thanks to step_by_step, kevinsogo and nhho for help in round preparation and testing the round.

UPD2: The results table!

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 EricHuang2003 6 150
2 JerryKFC 6 151
3 Lovely_qgq 6 170
4 Meroeht 6 181
5 MYTH_vs_REALiTY 6 209

Congratulations to the best hackers:

Rank Competitor Hack Count
1 djm03178 30:-2
2 2014CAIS01 13:-3
3 quailty 5:-2
4 Harmonium_Wale 4:-2
5 kimden 2

110 successful hacks and 226 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A jh05013 0:01
B JerryKFC 0:02
C GrayGlobe 0:03
D T______________T 0:21
E NamikazeBoruto 0:11
F Counting_Stars 0:20

UPD3: Editorial

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By vovuh, history, 6 years ago, In English

988A - Diverse Team

Tutorial
Solution (Vovuh)

988B - Substrings Sort

Tutorial
Solution (Vovuh)

988C - Equal Sums

Tutorial
Solution (Vovuh)

988D - Points and Powers of Two

Tutorial
Solution (Vovuh)

988E - Divisibility by 25

Tutorial
Solution (Vovuh)

988F - Rain and Umbrellas

Tutorial
Solution (Vovuh)
Solution (step_by_step)

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By vovuh, history, 6 years ago, translation, In English

Hello!

Codeforces Round 486 (Div. 3) will start on June 1 (Friday) at 14:35 (UTC). It will be the third Div.3 round in the history of Codeforces. You will be offered 6 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.

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 Maksim Neon Mescheryakov and Ivan BledDest Androsov for testing the round.

UPD: I also would like to thank step_by_step and eddy1021 for testing the round and help with it preparation!

UPD2: You will be given 6 problems and 2 hours to solve them.

UPD3: Editorial is published. Thanks to Mikhail awoo Piklyaev for the help with translation.

UPD4:

Congratulations to the winners (official results):

Rank Competitor Problems Solved Penalty
1 volamtruyenkyii 6 196
2 IOI2018 6 238
3 Student_of_Husayn 6 303
4 fshp971_ 6 311
5 Deadpool 6 313
6 Jajceslav 6 341

Congratulations to the best hackers:

Rank Competitor Hack Count
1 jhonber 70:-1
2 djm03178 61:-4
3 applese 53:-1
4 Midoriya095 41:-3
5 step_by_step 38:-5
6 greencis 57:-45

530 successful hacks and 401 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A Uzumaki_Narutoo 0:02
B Ad1let 0:06
C Ad1let 0:12
D volamtruyenkyii 0:23
E fafafa 0:19
F MuieEcaterina 0:49

I hope that you will like the problems. If the problems in this round are too easy or too hard, then we will adjust the difficulties in the next Div. 3 rounds.

Good luck!

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By vovuh, history, 6 years ago, translation, In English

977A - Wrong Subtraction

Tutorial
Solution (Vovuh)

977B - Two-gram

Tutorial
Solution (Vovuh)

977C - Less or Equal

Tutorial
Solution (Vovuh)

977D - Divide by three, multiply by two

Tutorial
Solution (eddy1021)

977E - Cyclic Components

Tutorial
Solution (Vovuh)

977F - Consecutive Subsequence

Tutorial
Solution (Vovuh)

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By vovuh, 6 years ago, In English

Hello!

Codeforces Round 479 (Div. 3) will start on May 6 (Sunday) at 14:05 (UTC). It will be the first Div.3 round in the history of Codeforces. You will be offered 6 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.

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 Neon for testing the round.

UPD: Thanks a lot to testers dreamoon_love_AA, eddy1021, step_by_step and Egor.Lifar who agreed to test the problems and found the mistakes. Now we are ready to start the round!

I hope that you will like the problems. If suddenly something does poorly with difficulties of the problems, then we will adjust the difficulties in the next Div. 3 rounds.

Briefly about myself. My name is Vladimir Petrov, I am studying at the 3rd year at Saratov State University and from the high-school I am studying at SSU Olympiad Training Center. In ICPC I participate in the team "Saratov SU Daegons" with awoo and Neon. I like reading and watching science fiction. I’ve read "Song of Ice and Fire" 3 times and wait for publication of 2 more volumes.

Good luck!

UPD2: Editorial

UPD3:

Congratulations to the winners (official results):

Rank Competitor Problems Solved Penalty
1 cMartynas 6 69
2 nimphy 6 117
3 Passenger 6 124
4 mandinga 6 128
5 raffica 6 144

Congratulations to the best hackers:

Rank Competitor Hack Count
1 greencis 36:-8
2 Tlalafuda__Tlalafu 10:-1
3 STommydx 9:-1
4 dalex 8:-7
5 dreamoon_love_AA 4:-3
6 shnk 2

97 successful hacks and 297 unsuccessful hacks were made in total!

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

Problem Competitor Penalty
A kuzmoid 0:01
B peach 0:04
C Milhous8 0:08
D Milhous8 0:11
E s0mth1ng 0:09
F DoveDragon 0:14

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By vovuh, history, 6 years ago, translation, In English

976A - Minimum Binary Number

Editorial
Solution (Vovuh)

976B - Lara Croft and the New Game

Editorial
Solution (PikMike)

976C - Nested Segments

Editorial
Solution (PikMike)

976D - Degree Set

Editorial
Solution (PikMike)

976E - Well played!

Editorial
Solution (Ajosteen)

976F - Minimal k-covering

Editorial
Solution (adedalic)

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