andr1y's blog

By andr1y, 7 weeks ago, In English

Hello. I am from Ukraine. I am sure that you know about the situation in my country and about things happening right now. Many people are giving infinitely valuable help to Ukrainian refugees, donating to UAF and simply helping spread the truth. I am sure we have such people also in our community. Ukraine, Ukrainians, and personally I appreciate your help highly. Thank you so heartily.

But now I am here to ask you, the Codeforces community, for help. There is no safe place in Ukraine right now — everywhere you might get killed by a missile strike, so holding the IOI selections is obviously impossible. Our dear friends from Poland decided to help us. They will organise everything for us, but they need money.

→ Click here to donate ←

Ukrainian competitive programmers are one of the most powerful cp-eps in the World. Our the most recent achievements:

  • Baltic Olympiad in Informatics — 4 gold medals, 2 bronze medals
  • International Zhautyk Olympiad — 2 gold medals, 3 silver medals, 7 bronze medals
  • Romanian Masters of Informatics — 2 gold medals, 1 silver medal, 6 bronze medals
  • International Autumn Tournament in Informatics — 2 gold medals, 3 silver medals, 3 bronze medals
  • European Girls Olympiad in Informatics — 1 gold medal, 3 silver medals
  • European Junior Olympiad in Informatics — 4 silver medals, 4 bronze medals
  • International Olympiad in Informatics — 1 gold medal, 2 silver medals
  • All-Russian Team Olympiad among Scholars — 1st absolute place, it was the first time when Ukraine team become the winner of this competition and one of a few times that has received a medal.

and so on...

Participation in the IOI is the most wanted dream for every competitive programmer in school times and Russia is trying to break this dream for each of us. But you can help. Everything is in your hands. If everyone, who reads this post, donates about 1 euro, the fundraising will end in 24 hours.

We need your help. Thanks in advance.

→ Click here to donate ←

upd: if you can't donate, help at least in sharing this post

upd2: updated link in the post to English version of the website

upd3: thanks to everybody for helping in any way!

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By andr1y, history, 5 months ago, In English

Do you play on a guitar? Does somebody among top coders play on a guitar? If you do, what is your favorite song? And, a little strange question, but which chord do you like the most?

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By andr1y, history, 6 months ago, In English

Hmm, it's time to update year in CodeForces code. Again.

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By andr1y, history, 10 months ago, In English

On today's CF Round #742, I submitted my code to the problem E, and suddenly got "Compilation Error", compile log informed me this thing:

Compiled file is too large [47861470 bytes], but maximal allowed size is 33554432 bytes [CompileRequest {id='program.cpp', description='', file='program.cpp', resources='', type='cpp.msys2-mingw64-9-g++17'}].

Submission: 127958200

I thought this is a system's bug, and resubmitted the code, and I got the same error: 127958576. After that, I saw that my binary file really is too large — about 44 Mb. I tried different things like getting rid of useless libraries or enabling optimization like Ofast/O3 etc. But none of this helped. After that, I wanted to replace all long longs except t_obj.ans with ints, but only separated ans from other variables and made tiny change ll ans=0; -> ll ans;, and compiled. It was really strange, but the binary file size became 36 Kb. To make me safe, I removed =0 from almost all variables and made a constructor, which makes them zero, and submitted that. It compiled well and passed pretests — 127960252.

So, the question is: how =0 near the variables can affect binary file size? This works only on GNU-based compilers? Can this behaviour be predicted, and can it be forced? Can I in such way reduce work time by increasing compile time?

Sorry for my bad English, thanks for any answer.

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By andr1y, history, 14 months ago, In English

Hello Codeforces, recently, there was a contest on CSAcademy named "FiiCode 2021 Round 2" and there was a task "Clown Fiesta", in a editorial for the task, there were lines such like:

If we take a sequence, where $$$a_0 = m$$$, $$$a_1 = \varphi (a_0)$$$, $$$a_2 = \varphi (a_1)$$$, $$$...$$$, $$$a_{k-1} = \varphi (a_{k-2}) \neq 1$$$, $$$a_k = \varphi (a_{k-1}) = 1$$$ and $$$m$$$ is prime number less than $$$10^9$$$, then $$$k$$$ will be not greater than $$$log_2(m)$$$.

Can someone prove it?

P.S. link to problem.

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By andr1y, 17 months ago, In English

Hello, Codeforces. Today I solved problems in problemset and found interesting thing. Well known that when you create problems in polygon you can set custom output to tests in statements. It is used in many problems where you must output algorithm to solve. But, when you submit your code, you can see your output to test and jury's answer. The custom output on examples is used so that the participant does not understand the algorithm for solving by examples, but the jury's answers can lead the participant to the correct algorithm. For example, lets see second test from problem 1479C - Continuous City.

The output in statements:

Spoiler

The output in submission:

Spoiler

As we can see, outputs differ. I think this is serious bug, which can lead participants to jury's algorithm, and this should be fixed asap

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By andr1y, history, 2 years ago, In English

MikeMirzayanov It's time to make year++ in CodeForces code :))

upd: it`s fixed now!

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