RDDCCD's blog

By RDDCCD, history, 5 months ago, In English

On the Global Round 31, user Su_Zipei has just used AI to make it to the top 20 of the contest.

Indeed, a smart contestant would not use overtly suspicious AI-generated code; those grey participants who rapidly solve the first six or seven problems in a competition can easily be identified as having used AI. A better approach is to obfuscate and polish the code provided by AI, or even rewrite it based on the AI's logic——for contestants with enough coding experience, this is quite straightforward. Clearly, compared to a 1200-rated player using AI to reach 1800, a 2400-rated player finds it easier to use AI to reach 3000.

Still, we can find some evidence that is not so convincing. For those people who solve problem H1 fast enough, Kevin114514 uses 36 minutes, tourist uses 42 minutes, ecnerwala uses 32 minutes, while other pariticipants solves it even longer(~1h). However, Su_Zipei only solve it in 19 minutes, which is really, really fast.

Another issue that requires attention is this code uses captital letter "MOD" for modulo number. This is a rather rare habit because you need to type a lot of "MOD", and holding down the shift key each time can be very annoying. In contrast, most AI-generated code uses uppercase "MOD". For comparison, this code and this code from the same contestant use p and mod as the modulus, respectively.

Of course, this evidence is not particularly strong. In fact, unless the user is extremely careless, it is difficult to find truly conclusive proof of AI usage. The reason I am writing this post is that I know this user offline and am clearly aware that he has previously used AI to participate in competitions. Given that AI is now sufficiently advanced, it is challenging to effectively ban its use in online contests. However, I hope to discourage situations where individuals rely entirely on "piloting" AI to achieve extremely high rankings. This requires joint efforts from both the community and the participants.

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By RDDCCD, history, 3 years ago, In English

Hello, Codeforces!

I'm very glad to invite you to participate in CodeTON Round 4 (Div. 1 + Div. 2, Rated, Prizes!), which will start on Mar/31/2023 17:35 (Moscow time).You will be given 8 problems and 2 hours to solve them. The round will be rated for everyone.

I'd like to give my sincere thanks to:

Hope everyone can enjoy the round!

UPD: The tutorial is here.

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 4.

The Open Network (TON) is a fully decentralized layer-1 blockchain designed to onboard billions of users to Web3.

Since July 2022, we have been supporting Codeforces as a title sponsor. This round is another way for us to contribute to the development of the community.

The winners of CodeTON Round 4 will receive valuable prizes.

The first 1,023 participants will receive prizes in TON cryptocurrency:

  • 1st place: 1,024 TON
  • 2–3 places: 512 TON each
  • 4–7 places: 256 TON each
  • 8–15 places: 128 TON each
  • 512–1,023 places: 2 TON each

We wish you good luck at CodeTON Round 4 and hope you enjoy the contest!

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By RDDCCD, history, 3 years ago, In English

A. Beautiful Sequence

Hint
Tutorial
Solution

B. Candies

Hint
Tutorial
Solution

C.Make It Permutation

Hint 1
Hint 2
Tutorial
Solution

D.Climbing the Tree

Hint
Tutorial
Solution

E.Monsters

Hint 1
Hint 2
Tutorial
Solution

F.M-tree

Hint 1
Hint 2
Tutorial
Solution

G. The Maximum Prefix

Hint
Tutorial
Solution

H.Last Number

Hint
Tutorial
Solution 1(floor sum)
Solution 2(fibonacci)

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By RDDCCD, 6 years ago, In English

This weekend, on Nov/24/2019 11:05 (Moscow time) we will hold Codeforces Round 602. It is based on problems of Technocup 2020 Elimination Round 3 that will be held at the same time.

Technocup is a major olympiad for Russian-speaking high-school students, so if you fit into this category, please register at Technocup 2020 website and take part in Technocup 2020 - Elimination Round 3.

Problem authors are me, nocriz, BledDest, adedalic and MikeMirzayanov. Many thanks to the testers: KAN, Supermagzzz, Stepavly, AdvancerMan and unreal.eugene!

Div. 1 and Div.2 editions are open and rated for everyone. As usual, the statements will be provided in English and in Russian. Register and enjoy the contests!

Have fun!

Scoring distribution:

Technocup: 500 1000 1250 (500+1500) 2500 (1000+2000) 3250

D1: 500 (500+750) 1500 (1000+1000) 2250 2500

D2: 500 1000 1250 (500+1500) 2500 (1000+2000)

UPD: Div1 Top5

1.sunset

2.tourist

3.WZYYN

4.EvenImage

5.OddImage

And congratulations for OddImage to be the youngest Legendary GrandMaster in the age of 14!

Div2 Top5

1.funtik

2.PureWhite

3.nehnait

4.Fuyuki

5.rama_pang

And also the Editorial is out.

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