Top Comments

And here's something special: Solve problems and make a difference! Yes, you heard it right, just like my last contest, this time as well you can help the world just by solving problems. I will donate money to the underprivileged people in my neighborhood based on the solve count of each problem by the following measure:

Donation Per AC

You can check how it went the last time I did this: https://codeforces.me/blog/entry/96333#comment-907470

Also, the top $$$5$$$ Bangladeshi contestants will receive $$$1000, 800, 700, 600,$$$ and $$$500$$$ BDT respectively from me as a small gift!

Note that neither TON nor Codeforces has anything to do with the donation or the gift.

Not me guessing difficulties by USD

I only received the message yesterday that YouKn0wWho's round requires an alternative problem, and the coordinator needs to select a problem from my round (which you previously coordinated). We are struggling with selecting problems and fixing bugs. We only confirmed the final problemset a few hours ago. And I expect to notify you after participating in today's codechef round. Overall, I apologize for not communicating with you in a timely manner.

On elsantodel90IOI 2025 Call for Tasks, 33 hours ago
+63

Submission deadline 29th December 2025 doesn't look right.

+51

Solutions (SubtasksWhere)

E (bincatmod)
C (Points and Threads)

Sorry, I overreacted. I didn't consider that the problem could have been just added......

As a tester, I can confirm that this round does indeed have problems.

toaster

+37

Don't worry, we will get the first place.

+31

遮沙避风了

+25

Don't worry, we(Objective-KUB1) will win Yokohama Regional.

On H_R_KMy luck.exe, 14 hours ago
+25

check my contest history to see what comes after 1599

There is a trick that still works at the time I write this message. You can append %3f to the url and it will load instantly.

On elsantodel90IOI 2025 Call for Tasks, 23 hours ago
+22

They might accept anything. In IOI there are easy problems and hard problems

Bro can't you read?

As a tester, I didn't know I could have won $15,000 (just needed to beat a certain Belarusian...)

Y'all should give it a shot!!! Good luck.

MAKISE KURISU!!!!

As a tester, I can confirm that I tested this round.

+18

Meaningless. Please don't waste your time. It's a waste of time to read your unreadable blog.

Thanks for the contest. QUICKEXIT was such a beautiful problem!

Unlike the TON round 8, 256-1023 places lose their prizes, and 20 USDT is much less than 8 TON (8 TON > 8 * $5 = $40 = 40 USDT), which 128-255 places got in round 8.

Their settlement is also without TON now.

What happened to TON?

BUMP

On DarkSilverDiameter of a graph?, 33 hours ago
+16

I'm pretty sure that in general graph you cannot do better than $$$O(N^2)$$$. Someone please correct me if I am wrong.

And is there a Euclidean Distance MST algo

On _Randooom_What ?, 45 hours ago
+14

I think the main reason your blog was downvoted is that I can do the same with the filter problem function.

As a tester, this is the $$$4^{th}$$$ time in a row I found at least one problem in the round I tested really satisfying, and I hope people would feel the same.

As a tester I wish good luck to everyone!

+14

遮沙避风了

change time/day icpc india clash

On SecondThreadHacker Cup Shirts 2024, 40 hours ago
+13

Kazakhstan is on the list now

Reminder: The contest starts in 30 minutes.

On _Randooom_What ?, 37 hours ago
+13

these kind of blogs are good, not all blogs on codeforces have to be useful and clever, a couple of them are just for fun and relaxation from tasks. I agree that second one is stupid, but the first one is pretty vital and funny

As a tester, hackerrank is kinda mid

Let me tell u sth about ArshiaDadras:

I officially started competitive programming and programming classes with Arshia Dadras four years ago. He is a very capable and ethical teacher. Thank you, Arshia, for being so great <3

+13

Reading this post was heartwarming. I'm glad you liked our problems, and I hope you get a top-200 shirt next year.

Meta has rejected my resume for SDE and MLE positions 12 times

I'm sad to see you had such a terrible experience with our recruiting team. Sometimes there are discrepancies between what the recruiters are focused on and what's ultimately in the long term best interest in the company. Sometimes there is just widespread systematic incompetence at making what seem like obviously good choices when there are lots of people involved in something big. I honestly have no idea how your resume got ignored 12 times. Obviously it shouldn't have. There's nothing I personally can do about it at the moment, but I just wanted to say I'm sorry, it's not your fault, and I'll do what I can to help our company make more reasonable decisions in the future.

why 256-1023 places no prize this time :(

Thank you so much for your kind words and support, AmirParsa!

It’s truly a pleasure to be remembered in such a thoughtful way. I’m also really happy to see that you’re continuing to improve your coding skills.

Wishing you the best of luck in your journey, and I hope we get to meet in person soon!

On H_R_KMy luck.exe, 7 hours ago
+12

I feel you.

On UTPC_AdminUTPC Fall 2024 Contest #5, 37 hours ago
+11

Thank you, I've just fixed it.

On _Randooom_What ?, 35 hours ago
+11

tbh im very shocked that blog became so popular, i posted it just for fun, but my friends liked the post, we just love memes about that, thats all

I struggled with ONETOTHREE during the contest and wondered why so many participants get AC with this problem, but after the contest, I noticed and was amazed that the following scheme is valid.

Spoiler

We can actually prove it by proving that we can never merge islands of 3's. (2's are fixed). I got 1e9+7 WAs before noticing that we have to run the loop backwards as well for smth like 233312 😭

if possible please change the time/date of the contest as icpc india preliminary contest will be held on the same day 23rd nov 21-23:30. so that we all can take part too!!

When I came up with the problem, I had a more complicated casework-y solution, and only later realized that the simple greedy implementation is actually correct.

I was not sure how guessable this was so I briefly considered modifying the problem to ask for the answer for every prefix or something like that, but after discussing with the tester we decided it's fine to keep it as-is, since for the most part I feel like if you're able to think of this algorithm then it's not too hard to prove it either. (Also it makes for a simple implementation which is always nice.)

I did make sure to modify the samples so that just iterating forward would pass them though :) (you're welcome RoomTemperatureIQ)

+10

Congratulations Screenwalkers! Our team(WayInWilderness) participate in Yokohama Regional from korea. So it would be fun watching the university of tokyo teams at scoreboard during the contest.

I see tourist registed for this contest!

On elsantodel90IOI 2025 Call for Tasks, 22 hours ago
+9

I've seen problems around 1500

On _Randooom_What ?, 45 hours ago
+8

After downvoting a blog/comment, it shows a triangle icon which you can click to report.

"When she is at position x with a jump power of k, she can jump to any integer position in the interval [x,x+k]."

It is clear that there is not a limit which stop Mualani jumping twice with the same distance.

On UTPC_AdminUTPC Fall 2024 Contest #5, 40 hours ago
+8

The link to the time says that the contest will be held on 06:00 (which should be 18:00)

Fixed time

I also need an official announcement :(

You can flex with "I have gold at an international olympiad"

On SecondThreadHacker Cup Shirts 2024, 35 hours ago
+8

I just copy pasted the text that they showed after i confirmed my order. That's why i used the quotes.

On al95ireyiz[SUGGESTION] Test Cases, 15 hours ago
+8

Yeah, I know the feeling. It’s so frustrating when you get “WA on test X” and all they show is some huge number instead of the actual test case. If they just showed the failed input, it’d save so much time and make debugging way easier. I’d rather figure it out myself than rely on the editorial, honestly.

On 4o2aOptimality of today's E problem, 10 hours ago
+8

l0l

Spoiler
On AkiLotusOn interactive problems, 3 hours ago
+8

People seem to not like problems that are different, and interactive problems typically have a different way than normally expected to solve. It requires a different mindset.

I think interactive problems are kind of fun. They can be frustrating, but they are unique.

People should just create habits for interactive problems, and continue with it as a normal problem. For me in C++, I just make sure to have cout << flush; and to comment out my fast IO. I don't know if that is even necessary, but I make that a habit for interactive problems and I never need to worry about the interactive part of the problem.

Thank you for reading this. I believe that if you struggle with what to do on the interactive portion of the problem, try a few interactive problems out. Try different ways of flushing the output, using the different types of input/output, etc. If you are comfortable with it outside of the contest, you can be comfortable with it inside the contest.

clashing with icpc prelims india

On SecondThreadHacker Cup Shirts 2024, 17 hours ago
+7

SecondThread I think there might be a bug in the form menu. I used tab to navigate to the next option, but it triggered submit instead. Now they confirmed it with an incomplete delivery information.

Why hackerrank instead of domjudge or codeforces?

This problem is the OV problem with $$$\log$$$ bits, it cannot be solved better than $$$\mathcal O(nv)$$$.

On H_R_KMy luck.exe, 14 hours ago
+6

Luck the matchmaker!!

+6

你说的挺完美,但肯定不对

+6

So why do you say you can't speak English but the sentence "I can't speak English" appears?

Best wishes to the round, contestants, and problem setters.

On SecondThreadHacker Cup Shirts 2024, 37 hours ago
+5

I believe FedEx wouldn’t ship from the US to Ukraine when the country list was compiled. I’m not sure if that has changed since. If so, our distributor’s website should be updated to reflect that.

On _Randooom_What ?, 35 hours ago
+5

привет легенда

Good to see that I finally get 7 stars after this contest. My profile

As an author, please give me T-shirt too.

Great initiative vai. Amder moto gorib newbie der jonno ontoto akta problem raikhen vai request. jeno akta holeo solve korte pari vai.

On hxu10My Meta hacker cup experience , 23 hours ago
+5

Congratulations sir. Can you share or tell any compiler which is useful to use in MHC, like to generate output for those long test cases. Me noob only uses codeforces custom test everytime ;)

The timing of this contest overlaps with the India ICPC Prelims, and I really want to participate in both. Unfortunately, I’m torn between the two. :'(

I believe the interesting question is whether it's possible to do it faster than O(n^2) due to the need to calculate distance between every pair of points, to which the following links may be useful:

manhattan

euclidean

As a tester, I liked to test my first round! :)

PS: If you win $15,000, please give me the T-Shirt, hahaha

On AkiLotusOn interactive problems, 3 hours ago
+5

Same here. I (almost) always define all query syntaxes into functions accordingly, then forget about them and do the problems proper.

+5

要不为啥以前打CF没问题

+5

Your saying is perfect,but 100% incorrect.

+4

It's the same in Korea, though. The Seoul Regional is prioritized over the others.

It's a memory misuse problem, it happens when b is just after a in memory so the data inside b will be overwritten so u need to be careful using scanf() .

On SecondThreadHacker Cup Shirts 2024, 36 hours ago
+4

Can I have this year's chart size for t-shirt please SecondThread ?

On H_R_KMy luck.exe, 10 hours ago
+4

Needed 87 but got 86? So close, even the universe was like, 'Let’s keep it interesting' lol

On Wang_XiaoguangKids, something to say., 110 minutes ago
+4

ChatGPT:

In English
In Chinese

Probably, run ./compile_cpp.sh in the terminal.

Let's look at "border" $$$(n, y) - (x, y) - (x, n)$$$. Any path from $$$(1, 1)$$$ to $$$(n, n)$$$ crosses it.

WLOG, let's say that the path crosses the border at cell $$$(x, y')$$$ where $$$y \le y' \le n$$$.

Let's find the minimum path from $$$(1, 1)$$$ to $$$(x, y')$$$. It's easy to see that we can go from $$$(1, 1)$$$ to $$$(x, 1)$$$ and then to $$$(x, y')$$$ since $$$\gcd(x, a) = 1$$$.

So, the path $$$(1, 1) - (x, y')$$$ goes through cell $$$(x, y)$$$ for any $$$(x, y')$$$.

Code For C
On RE_PrinceRating rollback?, 30 hours ago
+3

thanks guys for upvoting me :)

Wow, I chose to attempt G over F in the contest because I saw it had more solves...

it's genuinely easier if you knew what you needed in order to solve it though.

On elsantodel90IOI 2025 Call for Tasks, 23 hours ago
+3
On H_R_KMy luck.exe, 10 hours ago
+3

Congrats!

Same Same but Different!

On H_R_KMy luck.exe, 9 hours ago
+3

Same, I needed +70 for expert but got 1 less and then minus in next

:D
+3

Points and Threads
Note that it is possible to avoid using cht to eliminate a log factor (though it wasn't necessary to get AC)

Hint
On elsantodel90IOI 2025 Call for Tasks, 45 minutes ago
+3

chUoNgnn (gold IOI 2024)

Hopefully not a Math Chef today:)

As a taster, I found the problems very delicious.

On elsantodel90IOI 2025 Call for Tasks, 19 hours ago
+2

As a tester, I tasted many flavours from the problems.

Auto comment: topic has been updated by ArshiaDadras (previous revision, new revision, compare).

Sorry man, but I have to admit that I'm kinda glad you didn’t know that 🫂

On elsantodel90IOI 2025 Call for Tasks, 22 hours ago
+1

Easy in the sense? Can you tell the rating of easy problems in ioi comparing to codeforces problem rating? Because Div1A is also easy but not for all :)

On SecondThreadHacker Cup Shirts 2024, 20 hours ago
+1

Tunisia is not included in the delivery list, can you add it