Theo830's blog

By Theo830, 3 months ago, In English

Problems A, B, C, D1 and E were authored by me and Adam_GS authored D2 and F.

1903A - Halloumi Boxes

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Solution
Code (C++)
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1903B - StORage room

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Solution
Code (C++)
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1903C - Theofanis' Nightmare

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Solution
Code (C++)
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1903D1 - Maximum And Queries (easy version)

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Solution
Code (C++)
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1903D2 - Maximum And Queries (hard version)

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Solution
Code (C++)
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1903E - Geo Game

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Solution
Code (C++)
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1903F - Babysitting

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Solution
Code (C++)
jeroenodb's solution O(M log N)
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By Theo830, 3 months ago, In English

Γεια σου (Hello), Codeforces once again!

Adam_GS and I are glad to invite you to participate in Codeforces Round #912 (Div. 2) which will take place on Nov/30/2023 19:35 (Moscow time). Note the unusual start time of the round. As usual, this round will be rated for participants with rating lower than 2100.

Problems were created and prepared by Adam_GS and me. We tried to make them interesting, with short and clear statements. We hope that you will enjoy them!

I would like to thank:

  • ScarletS for amazing coordination of this round.
  • Adam_GS for joining as an author after testing the contest.

You will be given $$$6$$$ problems (and one subtask) and $$$2$$$ hours and $$$15$$$ minutes to solve them.

The score distribution will also be announced shortly.

Good luck and have fun!

UPD1:

Score Distribution: $$$500-1000-1500-(1500-2500)-2250-3500$$$

UPD2:

Editorial

UPD3:

Congratulations to the winners:

Div2:

  1. DoIodu123

  2. 69JohnMouse69

  3. transfeft

  4. vflower

  5. Top2Greece

Div1 + 2:

  1. Um_nik

  2. ecnerwala

  3. Ormlis

  4. tourist

  5. noimi

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By Theo830, 23 months ago, In English

Problem:

You have $$$n$$$ radio channels and $$$m$$$ conditions about them. ($$$1 <= n,m <= 100$$$).

You need to build exactly $$$2$$$ radio stations that have an equal number of radio channels and satisfy all the conditions.

A condition is in the form $$$A$$$ $$$B$$$ and it means that radio channels $$$A$$$ and $$$B$$$ can't be at the same radio station.

What is the minimum number of radio channels that will not belong in any radio station?

Example: $$$n = 5,m = 3$$$

Conditions:

$$$[4,2]$$$

$$$[3,4]$$$

$$$[5,1]$$$

The answer is $$$1$$$ since we can have the $$$1st$$$ radio station with radio channels $$$[1,4]$$$ and the $$$2nd$$$ radio station with radio channels $$$[2,5]$$$.

This problem is from a national competition in Cyprus. Can someone give a hint about the solution or maybe recommend a similar problem?

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By Theo830, 2 years ago, In English

Γεια σου (Hello), Codeforces!

Dremix10 and I are glad to invite you to the first Cypriot round Codeforces Round #747 (Div. 2) which will take place on Oct/08/2021 18:05 (Moscow time). Note the unusual start time of the round. As usual, this round will be rated for participants with rating lower than 2100.

Problems were created and prepared by Dremix10 and me. We tried to make them interesting, with short and clear statements. We hope that you will enjoy them!

I would like to thank:

You will be given $$$6$$$ problems (and one subtask) and $$$2$$$ hours and $$$15$$$ minutes to solve them. Scoring distribution will be announced later.

Good luck and have fun!

UPD1:

Score Distribution: $$$500-1000-1500-1750-(1000-1500)-2750$$$

UPD2:

Editorial

UPD3:

Div2:

  1. A-SOUL_Diana

  2. End.

  3. tuihuademing6

  4. OguriCap

  5. PATOLOVE

Div1 + 2:

  1. SSRS_

  2. tourist

  3. 244mhq

  4. hitonanode

  5. A-SOUL_Diana

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By Theo830, 2 years ago, In English

1594A - Consecutive Sum Riddle

Hint
Solution
Code (C++)

1594B - Special Numbers

Hint
Solution
Code (C++)

1594C - Make Them Equal

Hint
Solution
Code (C++)

1594D - The Number of Imposters

Hint
Solution
Code 1(C++)
Code 2(C++)

1594E1 - Rubik's Cube Coloring (easy version)

Hint
Solution
Code (C++)

1594E2 - Rubik's Cube Coloring (hard version)

Hint
Solution
Code (C++)

1594F - Ideal Farm

Solution
Code (C++)

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By Theo830, history, 3 years ago, In English

I found a cheater in yesterday's round. He/She was a tester and he/she submitted from another account.

parker0523 = shirakami_fbk

I am not 100% sure but the coding style + template is exactly the same. Also, the submissions of the account are really fast for a low CM and his submission on problem C is very weird(105687315).

Please MikeMirzayanov check this out.

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By Theo830, history, 3 years ago, In English

Problem: You have some sets and you want to check if set $$$B$$$ is subset of set $$$A$$$. You can erase or insert any element from any set. Let's say that $$$Q$$$ is the number of queries (check,insert or erase) and $$$Q <= 10^5$$$.

I think that may exist a solution using hash function. If you find the binary representation of all the sets (a bit is true only if it exists in the set) if there is a way to find the bitwise AND operation of two hash numbers then if $$$A$$$ & $$$B$$$ $$$=$$$ $$$B$$$ then $$$B$$$ is subset of $$$A$$$.

Any ideas about a solution?

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By Theo830, history, 3 years ago, In English

Codeforces recently added dates from the past contest at your contests page or in your rating graph!

Capture

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By Theo830, history, 4 years ago, In English

Today when I was looking at the submissions in problem 1381B - Разъединение I saw 300iq's and Benq's solution. Both submissions(87538626 , 87530540) has a for loop and it does some operations with a bitset in order to find if you can make the sum of some sizes of blocks equal to n. I have done the same solution however I use simple $$$dp[i][j]$$$ = if we can make the sum $$$j$$$ using only the first $$$i$$$ elements. I was wondering what is the time complexity of their dp. Any ideas?

Capture.png

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By Theo830, history, 4 years ago, In English

Does anyone know a side that I can submit for ejoi 2019?

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By Theo830, history, 4 years ago, In English

Because tomorrow is the BOI 2019 day 1 I want to ask if someone know if there will be live scoreboard. Thanks a lot.

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