vovuh's blog

By vovuh, history, 2 weeks ago, In English

I'm so thankful to all testers, especially to Gassa and Rox for their invaluable help!

1409A - Yet Another Two Integers Problem

Idea: vovuh

Tutorial
Solution

1409B - Minimum Product

Idea: vovuh

Tutorial
Solution

1409C - Yet Another Array Restoration

Idea: vovuh

Tutorial
Solution (Gassa)
Solution (vovuh)
Solution (Rox)

1409D - Decrease the Sum of Digits

Idea: MikeMirzayanov

Tutorial
Solution

1409E - Two Platforms

Idea: vovuh

Tutorial
Solution

1409F - Subsequences of Length Two

Idea: vovuh

Tutorial
Solution
Solution (Gassa, greedy, O(n^4))

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By vovuh, history, 2 weeks ago, translation, In English

Hello! Codeforces Round #667 (Div. 3) will start at Sep/04/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round. Also thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for the discussion of ideas and testing the round!

Good luck!

UPD: Huge thanks to Ivan Gassa Kazmenko for testing the round and fixing some issues with statements and the round in general! Also thanks to sladkayaKlubnichka, kocko, Ilya-bar and infinitepro for testing the round!

UPD2: Editorial is published!

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By vovuh, history, 6 weeks ago, In English

All ideas belong to MikeMirzayanov.

1399A - Remove Smallest

Tutorial
Solution

1399B - Gifts Fixing

Tutorial
Solution

1399C - Boats Competition

Tutorial
Solution

1399D - Binary String To Subsequences

Tutorial
Solution

1399E1 - Weights Division (easy version)

Tutorial
Solution

1399E2 - Weights Division (hard version)

Tutorial
Solution

1399F - Yet Another Segments Subset

Tutorial
Solution

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By vovuh, history, 7 weeks ago, translation, In English

Hello! Codeforces Round #661 (Div. 3) will start at Aug/05/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round. Also thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for the discussion of ideas and testing the round!

Good luck!

UPD: Huge thanks to Ivan Gassa Kazmenko for testing the round and fixing some issues with statements and the round in general!

UPD2: Editorial is published!

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By vovuh, history, 2 months ago, In English

All ideas belong to MikeMirzayanov.

1385A - Three Pairwise Maximums

Tutorial
Solution

1385B - Restore the Permutation by Merger

Tutorial
Solution

1385C - Make It Good

Tutorial
Solution

1385D - a-Good String

Tutorial
Solution

1385E - Directing Edges

Tutorial
Solution

1385F - Removing Leaves

Tutorial
Solution

1385G - Columns Swaps

Tutorial
Solution

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

<too-old-joke-about-copy-paste>

Hello! Codeforces Round #656 (Div. 3) will start at Jul/17/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round. Also thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for the discussion of ideas and testing the round!

Good luck!

</too-old-joke-about-copy-paste>

UPD: Also thanks to infinitepro for help with statements and testing the round!

UPD2: Editorial is published!

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By vovuh, history, 3 months ago, In English

1374A - Required Remainder

Idea: vovuh

Tutorial
Solution

1374B - Multiply by 2, divide by 6

Idea: vovuh

Tutorial
Solution

1374C - Move Brackets

Idea: MikeMirzayanov

Tutorial
Solution

1374D - Zero Remainder Array

Idea: vovuh

Tutorial
Solution

1374E1 - Reading Books (easy version)

Idea: MikeMirzayanov

Tutorial
Solution

1374E2 - Reading Books (hard version)

Idea: MikeMirzayanov

Tutorial
Solution

1374F - Cyclic Shifts Sorting

Idea: MikeMirzayanov

Tutorial
Solution

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By vovuh, history, 3 months ago, translation, In English

<almost-copy-pasted-part>

Hello! Codeforces Round #653 (Div. 3) will start at Jun/28/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round. Also thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for the discussion of ideas and testing the round!

Good luck!

</almost-copy-pasted-part>

UPD: Also thanks to ma_da_fa_ka for testing the round and special thanks to Dmitrii _overrated_ Umnov, Artem Rox Plotkin and, of course, Mike MikeMirzayanov Mirzayanov for discussing ideas and great help with round preparaion!

UPD2: Editorial is published!

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By vovuh, history, 4 months ago, In English

All problems, except the problem D, are mine. The problem D author is MikeMirzayanov.

1353A - Most Unstable Array

Tutorial
Solution

1353B - Two Arrays And Swaps

Tutorial
Solution

1353C - Board Moves

Tutorial
Solution

1353D - Constructing the Array

Tutorial
Solution

1353E - K-periodic Garland

Tutorial
Solution

1353F - Decreasing Heights

Tutorial
Solution

Read more »

Tutorial of div3 E-onwards #1
 
 
 
 
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By vovuh, history, 4 months ago, In English

<almost-copy-pasted-part>

Hello! Codeforces Round #642 (Div. 3) will start at May/14/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round. Also thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for the discussion of ideas and testing the round!

Good luck!

</almost-copy-pasted-part>

UPD: Thanks to ma_da_fa_ka, Jaydeep999997, abhishek_saini, infinitepro and socho for testing the round!

UPD2: Editorial is published!

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By vovuh, history, 4 months ago, In English

All problem ideas belong to MikeMirzayanov. And he prepared all problems himself. I just helped with testing, reviewing and tutorial writing.

1352A - Sum of Round Numbers

Tutorial
Solution

1352B - Same Parity Summands

Tutorial
Solution

1352C - K-th Not Divisible by n

Tutorial
Solution

1352D - Alice, Bob and Candies

Tutorial
Solution in O(n)
Solution in O(n^2)

1352E - Special Elements

Tutorial
Solution

1352F - Binary String Reconstruction

Tutorial
Solution

1352G - Special Permutation

Tutorial
Solution

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By vovuh, history, 5 months ago, In English

1343A - Candies

Idea: vovuh

Tutorial
Solution

1343B - Balanced Array

Idea: vovuh

Tutorial
Solution

1343C - Alternating Subsequence

Idea: vovuh and MikeMirzayanov

Tutorial
Solution

1343D - Constant Palindrome Sum

Idea: MikeMirzayanov

Tutorial
Solution

1343E - Weights Distributing

Idea: MikeMirzayanov

Tutorial
Solution

1343F - Restore the Permutation by Sorted Segments

Idea: MikeMirzayanov

Tutorial
Solution

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

<almost-copy-pasted-part>

Hello! Codeforces Round #636 (Div. 3) will start at Apr/21/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round. Also thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for the discussion of ideas and testing the round!

Good luck!

</almost-copy-pasted-part>

UPD: Also thanks to Sakhiya07, infinitepro and ma_da_fa_ka for testing the round!

UPD2: Editorial is published!

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By vovuh, history, 5 months ago, In English

1335A - Candies and Two Sisters

Idea: vovuh

Tutorial
Solution

1335B - Construct the String

Idea: MikeMirzayanov

Tutorial
Solution

1335C - Two Teams Composing

Idea: MikeMirzayanov

Tutorial
Solution

1335D - Anti-Sudoku

Idea: vovuh

Tutorial
Solution

1335E1 - Three Blocks Palindrome (easy version)

Idea: MikeMirzayanov

Tutorial
Solution

1335E2 - Three Blocks Palindrome (hard version)

Idea: MikeMirzayanov

Tutorial
Solution

1335F - Robots on a Grid

Idea: MikeMirzayanov

Tutorial
Solution
Solution (actually _overrated_, fastest O(nm log nm))

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By vovuh, history, 5 months ago, In English

<almost-copy-pasted-part>

Hello! Codeforces Round #634 (Div. 3) will start at Apr/13/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round. Also thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for the discussion of ideas and testing the round!

Good luck!

</almost-copy-pasted-part>

UPD: Also thanks to ma_da_fa_ka and infinitepro for testing the round!

UPD2: Editorial is published!

Read more »

 
 
 
 
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By vovuh, history, 6 months ago, In English

1328A - Divisibility Problem

Idea: MikeMirzayanov

Tutorial
Solution

1328B - K-th Beautiful String

Idea: MikeMirzayanov

Tutorial
Solution

1328C - Ternary XOR

Idea: vovuh

Tutorial
Solution

1328D - Carousel

Idea: MikeMirzayanov

Tutorial
Solution

1328E - Tree Queries

Idea: MikeMirzayanov and vovuh

Tutorial
Solution

1328F - Make k Equal

Idea: MikeMirzayanov

Tutorial
Solution

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

<almost-copy-pasted-part>

Hello! Codeforces Round #629 (Div. 3) will start at Mar/26/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

</almost-copy-pasted-part>

Thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for help with testing the round!

UPD: Also thanks to Vitaliy kuviman Kudasov for testing the round!

UPD2: Editorial is published!

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By vovuh, history, 6 months ago, In English

Suddendly, all ideas of this contest are mine. And I'm very sorry about one missing small test in the problem B. This is the biggest mistake I made during the preparation of this round.

1324A - Yet Another Tetris Problem

Tutorial
Solution

1324B - Yet Another Palindrome Problem

Tutorial
Solution

1324C - Frog Jumps

Tutorial
Solution

1324D - Pair of Topics

Tutorial
Solution

1324E - Sleeping Schedule

Tutorial
Solution

1324F - Maximum White Subtree

Tutorial
Solution

Read more »

Tutorial of Psycho Thriller Cap
 
 
 
 
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By vovuh, history, 6 months ago, translation, In English

UPD: Pay attention to the changed start time of the competition.

<almost-copy-pasted-part>

Hello! Codeforces Round #627 (Div. 3) will start at Mar/12/2020 16:05 (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. 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

</almost-copy-pasted-part>

Thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for help with testing the round!

UPD2: Editorial is published!

Read more »

 
 
 
 
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By vovuh, history, 7 months ago, In English

1311A - Add Odd or Subtract Even

Idea: vovuh

Tutorial
Solution

1311B - WeirdSort

Idea: MikeMirzayanov

Tutorial
Solution (n^2)
Solution (n log n)

1311C - Perform the Combo

Idea: vovuh

Tutorial
Solution

1311D - Three Integers

Idea: MikeMirzayanov

Tutorial
Solution

1311E - Construct the Binary Tree

Idea: MikeMirzayanov

Tutorial
Solution

1311F - Moving Points

Idea: vovuh

Tutorial
Solution (Fenwick tree)
Solution (pbds)

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By vovuh, history, 7 months ago, translation, In English

<almost-copy-pasted-part>

Hello! Codeforces Round #624 (Div. 3) will start at Feb/24/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

</almost-copy-pasted-part>

Thanks to Artem Rox Plotkin and Dmitrii _overrated_ Umnov for help with testing the round!

UPD: It turned out that in the problem C, such a test exists that the answer overflows 32-bit integer type (int). Since such a test was not in the test set, many participants made such a mistake. We decided to forbid such tests, additionally guaranteeing that the answer fits in int.

UPD2: Editorial is published!

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By vovuh, history, 7 months ago, In English

1296A - Array with Odd Sum

Idea: vovuh

Tutorial
Solution

1296B - Food Buying

Idea: vovuh

Tutorial
Solution

1296C - Yet Another Walking Robot

Idea: MikeMirzayanov

Tutorial
Solution

1296D - Fight with Monsters

Inspiration: 300iq, idea: vovuh

Tutorial
Solution

1296E1 - String Coloring (easy version)

Idea: MikeMirzayanov

Tutorial
Solution (dp)
Solution (greedy)

1296E2 - String Coloring (hard version)

Idea: MikeMirzayanov

Tutorial
Solution

1296F - Berland Beauty

Idea: MikeMirzayanov

Tutorial
Solution

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By vovuh, history, 8 months ago, translation, In English

<almost-copy-pasted-part>

Hello! Codeforces Round #617 (Div. 3) will start at Feb/04/2020 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 Daria ZeroAmbition Stepanova, Mikhail pikmike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

</almost-copy-pasted-part>

UPD: Editorial is published!

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By vovuh, history, 8 months ago, In English

Thanks to Rox and _overrated_ for help with problem ideas and preparation!

1294A - Collecting Coins

Idea: MikeMirzayanov

Tutorial
Solution

1294B - Collecting Packages

Idea: MikeMirzayanov

Tutorial
Solution

1294C - Product of Three Numbers

Idea: MikeMirzayanov

Tutorial
Solution

1294D - MEX maximizing

Idea: Vovuh

Tutorial
Solution

1294E - Obtain a Permutation

Idea: Vovuh

Tutorial
Solution

1294F - Three Paths on a Tree

Idea: MikeMirzayanov

Tutorial
Solution

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By vovuh, history, 8 months ago, translation, In English

<almost-copy-pasted-part>

Hello! Codeforces Round #615 (Div. 3) will start at Jan/22/2020 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 Daria ZeroAmbition Stepanova, 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>

This is unusual, but good news! Our friends at Harbour.Space have a message for you:

Hello Muscat

Hi Codeforces!

As a special prize for the Codeforces Round #615, we would like to invite the top 3 participants to take part in our Hello Muscat ICPC Programming Bootcamp, which will take place in Oman, from March 19 to March 25, 2020. The prize will cover the participation fee, accommodation, and half-board meals for the entire duration of the bootcamp (except flights)!

There are three requirements to satisfy:

  • You took part in at least 10 rated contests on Codeforces
  • Your max rating should be less than 1900
  • You should be eligible for ICPC and/or IOI 2020+
Fill out the form→

So unofficial participants are also in a game (if meet the requirements).

Good luck to everyone!

UPD: I want to thank Artem Rox Plotkin and Dmitrii _overrated_ Umnov for invaluable help with the round preparation!

UPD2: Editorial is published!

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