Vovuh's blog

By Vovuh, history, 11 days ago, In English,

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

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By Vovuh, history, 13 days ago, In English,

<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

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By Vovuh, history, 4 weeks ago, In English,

1118A - Water Buying

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

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By Vovuh, history, 4 weeks ago, translation, In English,

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!

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By Vovuh, history, 2 months ago, In English,

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

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By Vovuh, history, 2 months ago, translation, In English,

<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

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By Vovuh, history, 2 months ago, In English,

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

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By Vovuh, history, 2 months ago, translation, In English,

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!

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By Vovuh, history, 3 months 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, 3 months 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 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
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 hahahahaha111 0:13
F kuchnaahopaayega 0:16

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By Vovuh, history, 3 months 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, 3 months 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 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 Roman Ajosteen Glazov, Farkhod Farhod_Farmon 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 paulomirandamss12 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 Muhanad_Alwarareh 29
5 electrostrike 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 sorry_hater_snsd_is_good 0:01
B ajarindong 0:02
C BigDelta 0:15
D1 bin_0808 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, 4 months 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, 4 months 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 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 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 PikMike 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 Programmist_111 0:05
D Laggay 0:12
E Programmist_111 0:12
F1 happ1 0:29
F2 Radko 0:32

UPD2: Editorial is published!

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By Vovuh, history, 5 months 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, 5 months 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.

Read more »

 
 
 
 
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By Vovuh, history, 6 months 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 months 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 PikMike, fcspartakm, Ne0n25, BledDest, Ajosteen and Vovuh. Great thanks to our coordinator _kun_ 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, 7 months 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, 7 months 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 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 problem_destroyer420 5 209
2 syh0313 5 225
3 VinceJudge0 5 230
4 kredo 5 234
5 EctoPlasma 5 241

Congratulations to the best hackers:

Rank Competitor Hack Count
1 halyavin 506:-92
2 antguz 121:-20
3 YangYunFei 50:-11
4 UselessChallenger 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 kredo 0:03
C kredo 0:13
D NT_Master 0:17
E syh0313 0:43
F iamunstoppabIe 0:19

UPD2: Editorial is published.

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By Vovuh, history, 8 months 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, 8 months 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 PikMike Piklyaev, Maksim Ne0n25 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 mafagafogigante 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 shanghaiKingCsl 0:12
E1 Ka55un0 0:30
E2 Ka55un0 0:30
F shanghaiKingCsl 0:48

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By Vovuh, history, 8 months 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, 8 months 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 PikMike Piklyaev, Maksim Ne0n25 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 HighPressure 6 236
2 LividFox 6 237
3 Rzuji 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 ducdien2267 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 thidailoc 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, 8 months 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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