Hello Codeforces!

We are excited to invite you to compete in the California Informatics Competition (CALICO) Fall '23! The contest will start on Saturday, November 18, 2023 at 4:00 p.m. PT and will be 3 hours long. Registrations are now open and will be until November 15, 2023 at 11:59 p.m. PT, so register here while you can! The contest will take place virtually on our custom judge platform.

The California Informatics Competition (CALICO) is a semiannual team programming contest organized by students at the University of California, Berkeley. We create original problems to encourage students to grow their problem-solving skills and learn algorithms in fun and exciting ways. Check out our website to learn more about the contest and join our discord server to get announcements, make teams, hang out, and more!

The contest will be 3 hours long and you can compete solo or in a team of up to 3. There will be around 8-12 problems spanning a wide range of difficulty for all skill levels. Some problems will have bonus test sets, where more efficient or advanced solutions can earn additional points. At least one of the problems will be interactive. Anyone can compete, but only pre-college teams will be eligible to win prizes. Editorials for each problem will also be available after the contest. More details will be released as the contest date approaches.

These awesome problems and editorials are written, prepared, and tested by the CALICO Team, including Bungmint, plourde27, yjp20, ss1237, bradley.louie1, fatant, mudkip, alfphaderp, voidcs, vcivek, JayU_, skywire2000, and many more!

We’ve had a ton of fun creating these problems! We think there will be something interesting for everyone, regardless if you’re totally new or an experienced competitor.

Good luck on the contest!

Link to English flyer | Chinese flyer

Hello everyone!

I was wondering if anyone had any pointers or useful papers/resources/etc. for a problem I came across today. I tried googling about it for a while but couldn't find anything of much substance, so I decided to take it here. It's called the balanced max cut problem.

A rough description of the problem: You're given an undirected weighted graph $$$G = (V, E)$$$. You want to partition the vertices into $$$k$$$ disjoint components such that each component contains around $$$\frac{n}{k}$$$ vertices (let's say no component can contain more than $$$\epsilon \frac{n}{k}$$$ vertices for some specified $$$\epsilon \geq 1$$$). Find an (approximate) optimal partition such that the sum of edge weights between vertices in different components is maximized.

There are a fair amount of resources that give approximate algorithms solve the balanced min cut problem, which is the same problem as above except the objective is to minimize the sum of edge weights between vertices in different components, instead of maximizing it. However, I don't think they extend very well to the opposite version of the problem. If anyone has any thoughts or resources please do comment! And let me know if I should clarify the problem statement a bit more.

A friend shared this paper with me. It was published today, and seems to suggest that max-flow/min-cut can be exactly computed in almost linear time in the number of edges for general graphs.

I haven't gotten much time to read through it, but I thought it would be interesting to post it here for discussion.

Comment if you're taking! It will be held on January 22nd, 1 PM CT on Kattis. The online mirror will be there too hopefully; my college didn't register (Go Bears -_-) so I'll have to take it on there too.

Good luck to everyone! Comment if you're taking tomorrow!

Hi,

I was wondering where codejam problems from 2015 and before could be found. I know google changed their codejam website recently, and is still in the process of uploading all the old problems to the new website, and I think they might have taken the old archive down (or, at least, I can't find it).

Does anyone know a source where I can find the pre 2015 codejam problems?

For reference, the link I'm looking at right now is here: https://codingcompetitions.withgoogle.com/codejam/archive. As you can see, only post 2016 problems have been added.

Also, Kickstart has the same issue, so if anyone has access to those, that would be greatly appreciated.

Thanks!

Hello Everyone,

Are the seeds for the contests on CF-Predictor calculated correctly?

On a recent contest: many users (such as me) ended up getting negative delta even though we got a lower rank than our seed (meaning we did better than "expected"), which is contradictory.

Does CF-Predictor calculate the seeds based on registered participants and not those who actually took the contest (thus making it a bit inaccurate) or are rating changes a bit off for codeforces?

Hi Everyone,

Pardon me if this is the wrong place to post; I'm new with blogs and all, but felt like I could probably put it here.

I know there are lots of CF predictors out there that give you your expected delta based on your rank and seed in the contest. Has anyone made a predictor that would tell you what rank you would need to gain a certain delta?

Basically, is there any app that lets me input the participants of a contest to get my seed and a given delta value and outputs a predicted rank? For example, if I wanted +50 delta on the next contest, I could put those two parameters in and it would give me the expected rank I need to get that in contest (around ~400 or something).