oursaco's blog

By oursaco, history, 3 months ago, In English

I was looking around at my position in standings during systests and I noticed many of the low rated participants had nearly identical code for D2. Examples:

https://codeforces.me/contest/2002/submission/275809437

https://codeforces.me/contest/2002/submission/275816397

https://codeforces.me/contest/2002/submission/275809226

https://codeforces.me/contest/2002/submission/275826393

It seems like some high rated user leaked solutions of D2 and possibly E as well ([user:NikolaT] who has a clearly plagiarized D2 ac'ed E with weird variable names), and the cheaters have started reaching GM/IM perf.

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By oursaco, history, 8 months ago, In English

You can find the HPI 2024 Novice and Advanced division problems here:

https://codeforces.me/gym/105023 (Novice)

https://codeforces.me/gym/105022 (Advanced)

Hope everyone enjoyed the contest :)

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By oursaco, history, 9 months ago, In English

Hi Codeforces,

The Harker Programming Club is excited to welcome you to participate in the annual Harker Programming Invitational taking place on March 9th, 2024 at The Harker School, with an online mirror available for virtual participation. The theme of our contest this year will be “CS & Transportation.”

Contest Information

The contest will last 2 hours and be split into novice and advanced divisions. Participants may form teams of up to 3 people. The contest will be open internet and ICPC style.

Registration for in-person is available here.

The online mirror will be available here.

The problems were all created and prepared by oursaco, BossBobster, Rowlet1, jchen05, kujousara, 25JulianaL, 26brennar, and alex.huangf. We expect the difficulty range to be from around Div. 4 A to Div. 1 E.

Prizes

  1. The first place team will receive $100 per member.
  2. The second place team will receive $50 per member.
  3. The third place team will receive $30 per member.

Note that the prizes are identical for both Novice and Advanced divisions and only available for in-person precollege participants.

Logistics

Location:

  • The Harker Upper School campus (500 Saratoga Ave, San Jose, CA 95129)

Schedule (March 9th):

  • 8:00 — 8:30, Registration

  • 8:30 — 10:30, Contest

  • 10:30 — 10:45, Break

  • 10:45 — 11:30, Industry Panelists

  • 11:30 — 12:00, Break

  • 12:00 — 12:30, Awards

For more information, visit our website.

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By oursaco, history, 11 months ago, In English

Sorry for the weak pretests on A :(. We hope you enjoyed the round nonetheless.

1904A - Forked!

Idea: Apple_Method
Preparation: Apple_Method/oursaco
Analysis: lunchbox

Solution
Code

1904B - Collecting Game

Idea: oursaco
Preparation: oursaco
Analysis: lunchbox

Solution
Code

1904C - Array Game

Idea: lunchbox
Preparation: lunchbox
Analysis: lunchbox

Solution
Code

1904D1 - Set To Max (Easy Version) / 1904D2 - Set To Max (Hard Version)

Idea: oursaco
Preparation: oursaco
Analysis: oursaco

Hint 1
Hint 2
Solution
Code

1904E - Tree Queries

Idea: Apple_Method
Preparation: oursaco

Editorial 1:
Analysis: oursaco

Thanks to errorgorn for the solution!

Hint 1
Hint 2
Solution
Code

Editorial 2:
Analysis: willy108

Hint 1
Hint 2
Hint 3
Solution
Code

1904F - Beautiful Tree

Idea: Apple_Method
Preparation: oursaco
Analysis: Apple_Method

Hint
Solution
Code

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By oursaco, 12 months ago, In English

Note the unusual time of the round.

Hello Codeforces!

lunchbox, Apple_Method, and I are pleased to invite you to participate in Codeforces Round 914 (Div. 2) on Dec/09/2023 19:05 (Moscow time). You will be given 2 hours to solve 6 problems (and one subtask).

The round will be rated for participants of Division 2 with a rating lower than 2100.

We promise the statements will be clear and concise, suitable for AdamantChicken2 to read wink wink.


Also, we would like to thank:


We hope you will enjoy the contest and receive positive delta!

Scoring distribution

$$$500 — 750 — 1000 — (1250 + 750) — 2750 — 3500$$$

UPD

The editorial has been posted!

Congratulations to our winners!

Congratulations for our first solvers!

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By oursaco, history, 16 months ago, In English

Why are the rating pages looking like this now lol

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By oursaco, history, 18 months ago, In English

Two years, one hundred and five days, and fifty minutes ago from this very moment, I was unfortunately hacked for the very first time by the user dapingguo8. Imagine how traumatized pupil oursaco was at that moment. He did not know of the existence of hacks, and his singular solve during Educational Round 103 was suddenly taken away from him. That day, dapingguo8 was already master, and he was participating out of contest. However, he went out of his way to traumatize me, a poor pupil, new to the platform. Since then, I have set dapingguo8 as my eternal rival, and after one million, two hundred and three thousand, and seven hundred and eighty two minutes, I am now writing this blog proud to say that I have finally passed dapingguo8 in rating.

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By oursaco, history, 2 years ago, In English

I've been seeing a lot more contests being on weekdays rather than weekends recently. For example, the next four codeforces contests are all on weekdays. Is there a reason for this? Even if the number of people who can't take contests on weekdays due to school and such is in the minority, I don't see any harm in moving the contests to weekends when more people can take them.

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By oursaco, history, 3 years ago, In English

I've been working on an NTT implementation, which needs a big modulo in the form of x*2^k + 1. Does anyone know any mods of this form around 1e25. I rly don't want to use Chinese remainder theorem T-T.

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By oursaco, history, 3 years ago, In English
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By oursaco, history, 3 years ago, In English

Can someone plz recommend some problems involving using matrices on a segtree?

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By oursaco, history, 3 years ago, In English

Wouldn't it be great if codeforces had the option to sort comments by some metric such as time or upvotes? I know it's not necessary, but hey I'm lazy and it would save me a few scrolls. :D

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By oursaco, history, 3 years ago, In English

did codeforces just remove c++11 from the compile languages

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By oursaco, history, 3 years ago, In English

I know that you can extend BIT to do range min/max queries with two BITs, but is it possible to range update while doing min/max queries with BIT.

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By oursaco, history, 4 years ago, In English

I saw that a few people were hacking other people in the hacks tab of today's contest, but I can't figure out how to hack.

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