By Okrut, history, 2 days ago, ,

1362A - Johnny and Ancient Computer

Tutorial
Solution

1362B - Johnny and His Hobbies

Tutorial
Solution

1362C - Johnny and Another Rating Drop

Author: MicGor

Tutorial
Solution

1361A - Johnny and Contribution

Tutorial
Solution

1361B - Johnny and Grandmaster

Author: Okrut

Tutorial
Solution

1361C - Johnny and Megan's Necklace

Author: Okrut

Tutorial
Solution

1361D - Johnny and James

Author: Okrut

Tutorial
Solution

1361E - James and the Chase

Tutorial
Solution

1361F - Johnny and New Toy

Tutorial
Solution

• +209

By TimonKnigge, history, 12 hours ago, ,

Just a reminder that GCJ Round 3 is about an hour away. I don't think there was a reminder email and I only just realized this, hopefully this will save some of you too :-)

EDIT: Round is over, can discuss now.

• +186

By Radewoosh, history, 2 days ago, ,

There are many blogs on Codeforces, and most of them aren't very important a long time after publishing, like round announcements, saying "hello", asking for a better explanation of problem B than the one in the editorial, and so on. Among them, there are a few very interesting blogs that are a great resource of knowledge, like ODE by MiFaFaOvO, HLD by Vladyslav, suffix automaton by quasisphere or even Blogewooshes.

In my opinion, it would be great if there would be a special place for such blogs, accessible for example, by navigation bar, where they would be somehow sorted. It would be much easier to think "Let's learn something new!" and to do it. Also, probably Codeforces would have the greatest such base for competitive programmers. What do you think guys and MikeMirzayanov?

EDIT One more argument after thinking a bit more: of course there are a lot of papers, but everybody here knows that it's much easier for "us" to learn from blogs written by other competitive programmers. An example which comes to my mind: I've heard that parametric search sometimes isn't very popular in papers because it has something like $O(\log(limit$_$for$_$coordinates))$ and it isn't "proper" to have something like this in the complexity while ofc for us it's great and has a lot of usages. Competitive programming and paper-science differ a lot, so a base of knowledge for us would be great and we have a lot of it written and hidden, so why not organize it?

• +688

By _humble_fool, history, 31 hour(s) ago, ,

Hello everyone,

Crack me if you can! was held on Codechef on 05 June, 2020. It was held by a indiviual guy ameya13.

The question set contains 5 questions, out of which one shows wrong output for sample test cases (Tony and the triplets), another one have test cases out of constraints (BT engine) and one question have ambigious statement (Interview Day). I was unable to concentrate to read the last question (Pencryption Password).

There were many high rated participants like Egor, vladprog, alexwice and many other yelow-orange coders of Codechef community. Checkout the standings here.

Now, one noticeable thing is that there are many WA verdicts. (Of course, due wrong test cases). Still, mayur2305 and starkk99 managed to solved them without any wrong submission (also really fast) and got rank one and two respectively. Third rank holder was maoni, and this is his/her first contest using this ID. There are no previous submissions. ID was made for this contest.

Now the thing which bothers me is that organiser ameya13, and rank holders starkk99 and mayur2305 were teammates in many contests. Check here. Moreover starkk99 and organiser ameya13 are from the same college! (starkk99 edited his college information in codechef for this contest.)

I think this much evidence is enough prove that this round was full of cheating. All all this was done for 250 laddus! I request codechef admins and coordinators (vijju123, smit_mandavia) to cancel the laddus for this round.

Any edit suggestions are welcome.

Edit 1: Codechef link of the discussion: here.

Edit 2: Admins decison can be seen here.

• +106

By hossainzarif, history, 44 hours ago, ,

I am currently solving 1700-2000 rated problems. But, looks like it isn't helping me cause I end up going to editorial 50% of the time. I am also having trouble with dynamic programming problems. Solved around 20 dp problems and still facing difficulties finding the states and transitions.

What would be the strategy of my practice?? Help please.

• +86

By Qualified, history, 29 hours ago, ,

Mine was when I got a +45 rating change. Although that isn't a lot, I finally improved. Look at rating graph, kinda trash. I want to hear yours.

• +17

By yosupo, history, 5 weeks ago, ,

Hello, codeforces!

Today, I introduce yet another online judge, Library-Checker!

As the name suggests, the object of this site is checking your libraries. The problems are "Implement RMQ", "Enumerate Primes", "Exp of Formal Power Series", "Decompose a graph into three-connected components"... and so on.

All problems are managed by me. In other words, I'm the admin of this site.

Anything of problems (testcases, solutions, generator, ...) are managed in github. It means,

• Anyone can add problems add testcases. Already most of the problems are prepared by other competitive programmers.
• Testcases are stronger and stronger with time (ideally).

(For competitive programmers who can do "real" programming: Have you ever think that "I want to test my library in CI..."? This judge will achieve your hope! Please refer verification-helper)

• +421

By gabrielwu, history, 26 hours ago, ,

If you are interested in participating in the Montgomery Blair Informatics Tournament, which will be held online from 1:00-4:00 PM EDT on Sunday (6/7/20), please register at https://mbit.mbhs.edu/.

Teams of up to 4 are allowed! Anyone can compete, but only teams of US high school (or middle school) students can win Amazon gift cards for prizes:

• $50 per person for 1st place in Advanced Division •$25 per person for 1st place in Standard Division, 2nd place in Advanced Division, and 3rd place in Advanced Division

If you want to get a sense of what mBIT problems are like, take a look at the problems from our contest last November:

Message me or email mbit.organizers@gmail.com if you have any questions!

• +95

By pritishn, 2 days ago, ,

Hello everyone, This extension will modify the submit through file block in the problem page so that we can paste our code there and submit.

Of course , if you liked submitting through file then it's useless for you. It is made for those who have a habit of pasting code in the separate submit page.

It also redirects into a new tab and you don't have to open a new page every time you submit.
Thanks for reading and hope you like it.

UPD : I added the feature that now selects the code written in the text-area on clicking the submit button, So now it's easier to delete the previously written code.

UPD : I found link to another such tool : https://codeforces.com/blog/entry/66646

This extension is a much simplified version of the tool mentioned in the above blog.

• +161

By maroonrk, history, 12 hours ago, ,

We will hold AtCoder Grand Contest 045. This contest counts for GP30 scores.

The point values will be announced later. I hope we can decide the point values and the contest duration before long.

We are looking forward to your participation!

P.S. The AtCoder Race Ranking can be found here. I don't know who created this list, but I'd like to say thank you to them.