Hello Bufu, why is your name bufu and not Bufula or Bufudyne

Yes, Galen mentioned that problem in his blog

Same question

You don't need to guess the solution for this problem, and you don't need to rely on your intuition much to solve it either. It's a step by step observation based problem.

I have explained the thought process step by step here, https://codeforces.me/blog/entry/152775?#comment-1358632

Intuition is not the same as guessing. Yes, it's a problem solving skill, one that you can grow through practicing. But even intuition shouldn't be enough to find out the answer. If the problem requires you to intuitively guess the solution, and having you implement it without properly understanding why the solution worked, then it's a bad problem. Intuition or not, one should understand the solution one implemented, that's the essence of problem solving.

I disagree with you, guessforces problems are bad. Programming contests are meant to test your problem solving skills, and it should rewards problem solving abilities. Your ability to guess the correct solution right doesn't reflect your ability to solve problems.

I have seen fair share of bad problems, but C is not one of them. It's an observation based problem.

1) You need to visit each row and column, so n and a must be coprime, similarly m and c

2) If n and a is coprime, We know that after exactly n moves we will be back to row no 1. Similarly, other rows are going to be repeated every n moves

3) Now the problem becomes simpler, if we can prove that we can completely finish one single row, we can definitely finish every other row, since row and column movements are independent.

3) Let's assume that we go d->r->d->r.... after n down steps and n right steps we will be at a certain position in row no 1. let it be x1, just before the last right step, we will be at another position in row 1, let it be x2 = (x1 — b) % c. We can notice that this process will keep repeating after every n steps, shifting the values of x1 and x2 by the initially found value of x1. Now you get another subproblem, you need to figure out if given these conditions we can complete a row or not, which is not difficult to do. You can calculate for both possible ways to start, but proving for one is enough.

This is not a very math heavy problem. It's a number theory based problem, which is well within the bounds of CP and it is a topic you need to master to get good at CP. It is not very easy, but not too mathematically complex for CP either.

It's mostly numbers, logics and theories, so don't think it's anything vivid. Usually the difficult part is to maintain consistency as you are trying to remember too many things at a time

I don't know which category this falls into. Nonetheless, when I am solving a difficult problem, I am mostly doing things in my head, occasionally using a pad to write out proofs and important points. When I am making a deductive proof I go through things step by step in my head, and sometimes take notes. However, if the proofs are complex or I need to visualize something, I draw sketches and use pads. It's because visualizing problem solutions or keeping everything in memory is difficult and it's very easy to make mistakes wrong deductions if the solution is complex

I lost a 180+ day streak. But before that I also lost a 775 day streak, so now this feels normal :")

Great Job, I wish I could solve 3500s like you do

That's actually a very cool idea. We can even extend this process further.

We can train AI models to detect cheating based on the development timeline. People write code differently when they understand the solution and when the don't, or even when they understand the solution, but didn't came up with it themselves.

If successful, this could detect cheating with high accuracy. We could drastically reduce cheating, by simple making the process more difficult

Write the logs in encrypted form. (Similar to RSA). They won't be able to modify it meaningfully unless they have quantum computers. I also suggest that the logs should be written no in a straightforwardly structured manner, but in an informal manner. Because structured writing can make it easier to reverse engineer it

It's almost like I have gotten worse by practicing lol

-48

You are insane man. What is your longest streak? In your local time zone?

My sincere apologies, I didn't think my words would hurt your tiny fragile ego that much.

I bet that's chatGPT

Thanks for the suggestions

How did you get to 2300+ from 2000+?

I did for 775 days until my streak broke. Tho I would say it's not as great as yours

His contest history, practice history, contest submissions, everything is suspicious. I hope moderators will look into this issue

I use CF Getrating extension for chrome. It shows you the problem rating by default, optionally you can click "Show All Tags" if you are stuck

The addition of prior knowledge would be a great idea. I will finally be able to look at editorials without spoiling the problem

Okay, got the proof. You are actually talking about the highest leaf, I was a bit confused because I read lowest == deepest. Let the depth of leaf D, then the answer is either D or D — 1. It's because until D, the number of nodes per depth is non-increasing, after that it can be any arbitrary number. So, the condition may not hold. This is so much easier compared to this solution :3 If this was the intended solution I doubt it would have even half of the solves during contest.

Anyways, it's not a tie actually. I was wearing a "Punjabi", the collars are designed that way which makes it look like a tie. Technically, yes, it's built in. I was wearing a hoodie on top of the Punjabi in this photo

Can you give a proof why?

Is it still going to be in China?

I am surprised to see no MIT here

You too man. Thanks a lot

Yeah, they are all my accounts :3

The person I am referring to in this post is not actually active in codeforces anymore. She rarely solved problems in codeforces. So you won't recognize her id

Btw, are you referring to zzzzsust19

24 is not that many 1200s. You can't expect to just start solving and immediately get results. Moreover, how much time you are spending matters as well. In general it is suggested to try at least half an hour by yourself before taking help, personally I suggest two. For the difficulty I practice on, that's the time it usually takes for me to solve a problem on average. If that doesn't work, you can fine tune your difficulty to see what works. Balance between comfort zone and difficulty

Yes, thanks

It's okay mate, being busy is not a bad thing

Yes XD

It is out of tokens

If you are not LGM after your first contest, what are you even doing with your life

No, you don't. Look at rainboy. He is a GM and he doesn't solve 800s

I need to see my solve counts after every problem I solve to stay alive

That's pretty cool

I need a gf who loves CF

Yes, there should be a command for that in TLE. For example:

;stalk AshrafSustS19 r>=2000 r<=2000

Hardware level detection is a bad idea for universities. We have dedicated CP community and labs in our university. One user cheating from one of these pcs would make it obsolete for many others. Similar issue could arise with cyber cafes and other public labs.

Moreover, CP is not like gaming. We will have to ban devices based on user ID. CP doesn't require any high tech hardware like gaming. You don't even need PCs to work with. You can code in one device while cheat from another. Effect of hardware ban is going to be much more complicated than for video games. A simple example, I can easily take part in a contest from someone else's PC. But if I want to play an online game using cheat detection, say valorant. I can't just go open a random PC and start valorant. This makes experimenting a lot easier.

The biggest issue is detection. If we could detect cheaters easily, there wouldn't have been nearly as much cheaters as we see today. But currently we have nothing that can detect well enough if someone solve a problem by itself or used AI tools. As long we don't solve this, no matter what we do, is going to turn obsolete.

Defylogicguy bro, that defies logic

What is division 3?

I think one thing that might help reduce cheating, is that like we have problem testers for contests, we can maintain AI testers. They would try to have the AI models solve the problem. This can help make cheating harder.

Yes.

But I would rather solve 1 2500R problem than 5 2100 problems

Around 60+ I would suggest. It varies

1. SUST_Migrosena AshrafSustS19 AlveRahman Abdullah500

I am I am too

Yes! Took a while, but I did it.

I replaced 4 modulo operation with 1 in my solution. And it got passed

Why do I have to go through such a long and convoluted process to just upload a submission? This is annoying

It's the emo emoji. It means the guy is probably an emo

"Legend"

If it was back then when I was still grey, I might have said me. But now I have become wiser, so I know not me

Dude just said "Maybe bad news for cheaters". He didn’t say that's the most serious issue to worry about. You are overreacting.

Also, as much I appreciate freedom of speech, considering how ignorant and gullible people are, freedom of speech should be regulated. Even in real life, because you are given freedom doesn't mean you can do whatever you want. If you steal and get punished for, you don’t say that's a violation of my freedom. Freedom of speech, like every other freedom, should be regulated. The real concern should be who are those people regulating it, and what is being regulated

The thing is, they are looking for candidates with rating like 1900+, but they themselves are under-qualified for that. Imagine an expert/slpecialist interviewing a CM :3

This post has aged like fine wine, I still remember all the comments claiming that "my submissions are fake", "I am a cheater". It feels pretty satisfying. Also, I feel flaterred that bigSchrodinger called my "Bangladeshi Tourist". BD Tourist should have become a GM by now, sorry I didn’t live up to your expectations

I didn't preprocess GCD, my solution got passed

My solution was O(n^3), it didn't pass. Slightly less than that actually

https://youtu.be/ceaD4EtbNMM?si=GVJFckcCMyTTbIZy

This video supposedly leaked the solution for D2, It was leaked around last 15-20 minutes, around that time D2 got a surge of submissions. That explains why do we suddenly see so many cheaters

If most of them have registered 6 months — years ago, and they have been cheating for all this long, it makes less sense that they would be stuck into ranks like pupil/specialist for this long. Furthermore, cheaters usually stop taking part in contests once they achieve a certain rating threshold, usually expert. Thousands of cheaters in the cheating groups are not necessarily active contestants, most of them probably left CP after they achieved their threshold level. Of course, 2000 cheaters didn't just spawn randomly out of nowhere. But to understand why we see a sudden cheating surge, we first need to know the exact context behind it. I have heard that the solutions were leaked by some livestream video or blog or something. If that is the case, then this sudden rise is actually not surprising.

Yeah, probably, if those 2000 people appeared out of nowhere, they might disappear out of nowhere!

Why do we suddenly have 2000 cheaters? Without knowing the proper context, it's naive to assume that 2000 people are going to cheat every round. If the solution to a problem is being leaked by some livestream/blog/youtube video, and mass people have access to it. People are going to cheat, specially when they see everyone else doing so. There's certainly a problem, but the problem is not 2,000 people cheating, it's mass people having access to cheating.

I am not expecting it to fall down. This sounds like an anomaly towards me. Because it happened with this contest, it doesn’t mean it is to happen every time. Ofc, actions need to be taken so it doesn’t become normalized

That's one round, how many rounds do you get 2000 cheaters on? Your being stuck in expert/specialist/pupil isn’t because of cheaters cheating in contest

You are overestimating the impact of cheaters on your performance. The only reason it has made so hard for you to enjoy CP is because you have allowed it to become such a big deal to yourself. Focus more on practicing solving actual good problems. If what is shown in your profile is all you have practiced, then you haven't nearly tried hard enough to complain about anything

Cheaters should be punished. But he is right

Also- 1) I'm bad at guessing 2) I am slow, at least comparing others my level, My div2 A, B, C solutions take longer than most people at my level, even slower than many experts 3) I also don't have a GM/non-GN friend to leak solutions to me

And I still got to 2000+. You need to get better at solving high difficulty problems, i.e: 1900-2200

Maintain stack. Randomly choose an operation to add a forward bracket or reverse bracket. When you add a forward bracket, add it to the stack. Add a reverse bracket only if there is at least one forward bracket in the stack. And in that case remove one forward bracket from the stack. In order to maintain a size limit, note that a bracket sequnce of size 2n has exactly n forward brackets. So use it to restrict the length of the sequence.

What anime is this

CF Peak: 2077, Lichess: Less than 1000 :3

Because your "beating around the bash" didn’t work, doesn’t make it a bad problem

When are we getting rating updates? it’s been over a day already

When are we getting the final results? Have the submissions been rejudged yet?

I'm in

It doesn’t have anything to do with "obvious answer".

He didn't ask anything stupid. Maybe he is feeling uncertain and looking for encouragement. That is perfectly fine.

What's up bigSchrodinger

Btw, congrats on CM

Ok, lmao

Great template. It would be nice if we could debug Structs as well. Is it doable?

AshrafSustS19

I don't know if I am qualified to call myself a high rated programmer or not. But I have never done any math contests. I barely did the minimum practice needed to prepare for exams in high school and never had particularly impressive score at maths. In fact, I had participated in zero extra-curricular activities before university.

However, one thing I did, when I did practice, was that I used to spent hours upon hours on a single problem. I rarely used to rely on textbook/guides. That habit of mine got carried into competitive programming, and that helped a lot.

Here is my take, problem solving is like an art. Following a rigid structural method is not really a good or reliable way to become a good artist. Art requires creativity. Likewise, problem solving requires creativity.

Therefore, to be a good competitive programmer, along with some conventional approaches, I suggest one should try-

1)Instead of focusing on rating too much, enjoy the process of problem solving itself. Enjoy the journey, not the destination.

2)Unbound one's creativity. I never used to limit my thinking, I used to try out ideas no matter how ridiculous they seemed to sound like, even if they seemed unfeasible at first. In fact, many of the solutions I figured out came from ideas which at least, in the beginning seemed unfeasible.

Solve more hard problems, maybe?

You can compare your solve graph with mine, it's not much better than my counts tbh.

People below 1600 aren't allowed to participate in the Div2. That's why everybody you see registering in Div2 are 1600-2099. Btw, it's similar to how in parallel Div2+1 contests 1900R+ rated users can't participate in Div2 contest

He needs to become a communist, that's why so many Chinese are red

Take some anti-depressants, you would be out of blue hopefully.

Bro, can you update this post to "How to become Master"? :3

You can also use these extensions if you use Chrome/firefox, CF analytics, Codeforces practice Tracker, CF predictor. Also there is a discord group by Errichto which provides lots of bot features that gives you some more options to try out

Yes, I do take notes for problems which I find important. I also have a to-do list for problems which I intend to do latter, or problems which I think I should try again.

Yes, 3 hours on average isn't enough for contest. I need to bring it down to 1

I don't remember the exact experience, but initially it would take me entire day to solve each problem, which has right now come down to around three hours. But overall, I rarely ever solved any problems in less than two hours. The overall three hours average is excluding those problems which took me days to solve. Of course, I didn't spend whole days on the very hard problems. But these problems probably took me 8+ active hours at least. Also, since I avoid editorials, I also have many unsolved problems in my sheets. Overall 10-15% of the problems I attempted are still unsolved. But I had the most fun solving 2200s so far. Most of the problems I solved required very sharp insights and observations, and also creative solutions. The last time I had this much enjoyment was when I was solving 1900s.

My teammate named our team "Late for Registration" lol. I don't have high expectations for this ICPC tho, this is only my second offline contest. So in this regard I am the least experienced in my team

To have haters is an achievement itself XD

Should be less then 5

Thanks vai/apu

This is dumb, I am too old for pointless conversations.

And I meant I have been practicing 2200s for much longer time than the time I have been consistently performing on CM level. Whatever he is trying to say, it is either dumb or irrelevant

CM starts at 1900, not 2000. You are talking about 2100s, not 2200s. 2200s are significantly more difficult even than 2100s. I have solved plenty of both of them, I know the difference.

Thanks a lot, I agree with you. The biggest benefit from solving all these problems was the experience and knowledge I learnt, which helped me solve relatively lower rating problem with much more ease than before. For example, before I solved them, on average it would take me 3 hours to solve a single 1900R problem. Afterwards, it came down to one hour.

Thanks <3