Hi all,

The second contest of the 2022-2023 USACO season will be running from January 27th to January 30th. Good luck to everyone! Please wait until the contest is over for everyone before discussing anything contest-related (including but not limited to your scores or anything about the problems).

For those unfamiliar with the USACO contest format, please refer to the contest instructions and rules. We provide a short FAQ but folks should read all the rules carefully.

I have a question about the contest. Where do I ask it?

Email the contest director via the instructions above. Do not post anything publicly about the questions (including but not limited to your scores, how you felt about the problems, any content of the problems, etc) until after the contest is over for everyone. Do not DM me or anyone else affiliated with USACO, only the contest director can assist you. The contest director does not monitor Codeforces, this blog post is merely a courtesy to inform other people of the contest.

When can I enter the contest?

The contest will open on January 27th. A link to the contest will be posted here shortly after the contest opens.

If I submit multiple programs, which one gets evaluated?

Only the last submission will be evaluated for official scoring purposes.

Can I use prewritten code / templates?

No.

Am I allowed to use outside resources during the contest?

You may only refer to language documentation.

Why didn't I get an email from USACO when I registered my account?

Follow the directions on the USACO website regarding Gmail Delivery Issues to contact the contest director.

Can I solve problems in Rust?

No, the only languages supported are C, C++, Java, and Python. Consult the instructions for language-specific technical details.

Will Rust support be added?

Petition IOI to add Rust support first.

Hi all,

The first contest of the 2022-2023 USACO season will be running from December 16th to December 19th this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing anything contest-related (including but not limited to your scores or anything about the problems).

For those unfamiliar with the USACO contest format, please refer to the contest instructions and rules. We provide a short FAQ but folks should read all the rules carefully.

I have a question about the contest. Where do I ask it?

Email the contest director via the instructions above. Do not post anything publicly about the questions (including but not limited to your scores, how you felt about the problems, any content of the problems, etc) until after the contest is over for everyone. Do not DM me or anyone else affiliated with USACO, only the contest director can assist you. The contest director does not monitor Codeforces, this blog post is merely a courtesy to inform other people of the contest.

When can I enter the contest?

This contest runs until December 19th, 23:59 UTC-12 and is four hours long. The URL for the contest page can be found here.

If I submit multiple programs, which one gets evaluated?

Only the last submission will be evaluated for official scoring purposes.

Can I use prewritten code / templates?

No.

Am I allowed to use outside resources during the contest?

You may only refer to language documentation.

Why didn't I get an email from USACO when I registered my account?

Follow the directions on the USACO website regarding Gmail Delivery Issues to contact the contest director.

Can I solve problems in Rust?

No, the only languages supported are C, C++, Java, and Python. Consult the instructions for language-specific technical details.

Will Rust support be added?

Probably not. Petition IOI to add Rust support first.

Hi all,

The final contest of the 2021-2022 USACO season will be running this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing anything contest-related (including but not limited to your scores or anything about the problems).

Is there a released PDF of the problem statements? The published link on the website 404's, it is possible to download the full Polygon package and get TeX statements that way but it does seem bad to have links on the website that are 404'ing.

(Incidentally, will this contest get uploaded to the CF gym? I recall old Northern subregionals being uploaded but don't seem to see this one either.)

Hi all,

The third contest of the 2021-2022 USACO season will be running from February 25th to February 28th this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing anything contest-related (including but not limited to your scores or anything about the problems).

Hi all,

The second contest of the 2021-2022 USACO season will be running from January 28th to January 31st this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing anything contest-related (including but not limited to your scores or anything about the problems).

Hi all,

The first contest of the 2021-2022 USACO season will be running from December 17th to December 20th this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Edit 1: The contest is live now! Please read the contest rules carefully, especially regarding how to ask clarifications or contact the contest organizers. Do not spoil anything (including but not limited to your scores or anything about the problems) about the contest until the end of the contest (four hours after the stated deadline of the contest).

Edit 2: Results have been released.

On szkopul, I'm seeing problem statements where the \n character appears instead of actual newlines, even in sample input/output. Other non-ASCII characters appear to be written in escaped format also instead of rendered properly.

I'm curious if this is a local issue for just myself and, if not, if anyone has a good short-term fix for this.

Problem statement

This problem looks like a fairly standard tree DP problem, I won't spoil the solution in case people want to think about it.

However, the reason why this problem is interesting (or perhaps extremely painful) is that the memory limit is 32MB. Given that $$$N$$$ can be 1.5 million, this means you're not even allowed to store $$$6N$$$ 32-bit integers.

Therefore, it seems that the main challenge of this problem is to be able to fit everything inside such a tight memory limit. Notably, I've gotten MLE just trying to read in the input and trying to get the tree stored in a representation that makes it possible for me to start working on the DP part of the problem.

In the modern era, memory limits are no longer this tight, but a lot of problems on szkopul retain these tight memory limits which occasionally makes it an interesting (or perhaps extremely painful) challenge to figure out how to fit things in the memory limit.

What's intended here? I asked about this problem in the AC server and got some advice with things such as relabeling the tree with ETT or simulating DFS without an explicit stack. It feels like the authors intended for some precise $$$5N + \mathcal{O}(1)$$$ memory solution and it's a little alarming that I can't even get beyond "read the input and come up with some representation for the tree" without getting MLE.

Hi all,

The final contest of the 2020-2021 USACO season will be running this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Hi all,

The third contest of the 2020-2021 USACO season will be running from February 26th to March 1st this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Hi all,

The second contest of the 2020-2021 USACO season will be running from January 22nd to January 25th this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Edit 1: The contest is now live! Please do not spoil anything about the contest publicly until the contest is over for everyone, and please report any issues with the contest directly to the contest administrator via the instructions instead of posting them here.

Hi all,

The first contest of the 2020-2021 USACO season will be running from December 18th to December 21st this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Edit 1: The contest is now live! There are new changes to how USACO contests are run — the most notable change is that I/O is no longer done via files. Please consult the official rules for all the changes.

Edit 2: Although the contest window is almost over, please do not discuss the contest until everyone has finished it. The contest window should close four hours after it officially ends since folks who join at the last minute purportedly still get a full window, in which case the contest ends at this time.

Edit 3: The contest is officially over — hope everyone enjoyed the contest! Results should hopefully be ready by the end of the week.

Edit 4: Results are out!

Hi all,

The final contest of the 2019-2020 USACO season will be running from March 27th to March 30th. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

The 2020 ICPC North America Championship 2020 is today!

The 60 best teams from North America will compete for the title of North America Champions, a trophy and also an opportunity to represent North America at the ICPC World Finals 2020 in Moscow, Russia! Join us for a live broadcast or just follow the contest through all the possible links below.

Today's live broadcasters will be ecnerwala, scott_wu, tehqin, and xiaowuc1. Live commentary will start at 10 AM EST!

Official Website: https://nac.icpc.global/

Hashtag: #icpcnac2020

Discord: https://discord.gg/FpJfBHS

Mirror contest: https://open.kattis.com/contests/nac20open

Scoreboard: http://nac.icpc.global/scoreboard/

Live broadcast: https://www.youtube.com/channel/UC6-6qLP8Fubg5F3r4tfbosw and https://www.twitch.tv/icpclive

Twitter: https://twitter.com/IcpcNac

Facebook: https://www.facebook.com/na.icpc.io

Flickr: https://www.flickr.com/photos/187051365@N06/

Hi all,

The third contest of the 2019-2020 USACO season will be running from February 21st to February 24th. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Some of the North American ICPC teams were upsolving NWERC 2011 and on problem G ran into issues where Bellman-Ford would not properly detect the presence of a negative weight cycle. Here's an example of a submission that uses Floyd-Warshall with no epsilons and gets AC, and here's an example of a submission that uses Bellman-Ford with no epsilons and gets WA. I believe that Bellman-Ford gets AC with no epsilon if you use long double.

The problem statement has this claim that an error of magnitude less than 1e-7 in one distance computation will not affect the answer. What is the proper way to interpret this claim in the context of implementing a solution to this problem? Furthermore, is the Bellman-Ford algorithm actually not robust in this manner, whereas Floyd-Warshall is robust?

Hi all,

The second contest of the 2019-2020 USACO season will be running from January 17th to January 20th. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Edit 1: The contest is now live! Please do not spoil anything about the contest publicly until the contest is over for everyone, and please report any issues with the contest directly to the contest administrator via the instructions instead of posting them here.

Edit 2: Due to a configuration error, the contest is running for 12 more hours than originally stated. The contest window is still open, please wait for the window to expire at 4:00 AM UTC on January 22nd before discussing.

Edit 3: Results can be found here.

https://zibada.guru/finals/ is a good resource up to 2008, but do such detailed scoreboards exist pre-2008? The ones that the ICPC website releases leave much to be desired in terms of which problems were solved, when, and by which teams...

Hi all,

The first contest of the 2019-2020 USACO season will be running from December 13th to December 16th this weekend. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Edit 1: The contest is now live! Please do not spoil anything about the contest publicly until the contest is over for everyone, and please report any issues with the contest directly to the contest administrator via the instructions instead of posting them here.

Edit 2: Even though it is impossible to start the contest after 23:59 UTC-12, contestants who start right at that point in time still get a full four hours to do the contest. Therefore, please do not discuss the contest until 4:00 UTC-12 on December 17.

Edit 3: Results can be found here.

Hi all,

The final contest of the 2018-2019 USACO season, the US Open, will be running from March 29th to April 1st! Good luck to everyone! As a courtesy to your fellow contestants, please wait until the contest is over for everyone before discussing problems here.

Edit 1: The contest is live! Please do not post any spoilers about the problems publicly — if you have any issues with the problem statements, please follow the instructions to voice your concerns.

Hi all,

The third contest of the 2018-2019 USACO season will be running from February 22nd through February 25th, and will be the final regular contest before the US Open. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Edit 1: The contest will open soon! If you see any issues with any of the problems, please follow the instructions here letting the contest director know what issues you have. Please do not complain about them on this blog post — that may spoil the problems for other contestants and it will not result in your issues being resolved. Good luck to all contestants!

Edit 2: The contest will end in under 24 hours! As a reminder, since all contestants get a full four hour contest window irrespective of when they start, please hold off discussion of the contest until everyone has finished the contest (4 AM UTC-12).

Hi all,

The second contest of the 2018-2019 USACO season will be running from January 18th to January 21st. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

EDIT: As a reminder, do not post any spoilers until the contest is over, which will be at 4 AM UTC-12 on January 22nd. If you have any issues with the problem statements, please consult the rules on how to contact the contest administrators. The administrators do not monitor social media.

Hi all,

The first contest of the 2018-2019 USACO season will be running from December 14th to December 17th. Good luck to everyone! Please wait until the contest is over for everyone before discussing problems here.

Some friends have reported that https://www.lydsy.com/JudgeOnline/registerpage.php is no longer working. Is this intentional?