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Agnimandur's blog

By Agnimandur, history, 2 months ago,

All problems were created and prepared by me and magnus.hegdahl. Thanks to BucketPotato, Monogon, and Priyam2k for valuable feedback and testing. Special thanks to MikeMirzayanov for coming up with the idea and preparing the unique checker for 1663H - Cross-Language Program. I hope you enjoyed the contest, and found it to be an interesting series of puzzles.

Example solution code written by Agnimandur is provided for each problem.

1663A - Who Tested?

Clue 1
Clue 2
Solution
Solution Code (Python)

1663B - Mike's Sequence

Clue 1
Clue 2
Clue 3
Solution
Solution Code (Python)

1663C - Pōja Verdon

Clue 1
Clue 2
Solution
Solution Code (Python)

1663D - Is it rated - 3

Clue 1
Clue 2
Solution
Solution Code (Python)

1663E - Are You Safe?

Clue 1
Clue 2
Solution
Bonus Clues (for other problems)
Solution Code (C++)

1663F - In Every Generation...

Clue 1
Clue 2
Clue 3
Solution
Solution Code (Python)

1663G - Six Characters

Clue 1
Clue 2
Clue 3
Solution
Solution Code (Python and Javascript)

1663H - Cross-Language Program

Solution

• +92

By Agnimandur, history, 2 months ago,

With Nickolas not writing a contest this year, magnus.hegdahl and I have decided to take up this sacred duty :). We would like to invite everyone on Codeforces to the April Fools Day Contest 2022. Special thanks to BucketPotato for volunteering to test this contest!

The 10th April Fools Day Contest will take place on Apr/01/2022 17:35 (Moscow time). This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.

In this round you'll be given several weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the contests of the past years: 2012, 2013, 2014, 2016, 2017, 2018, 2019, 2020, 2021.

Good luck, and have fun!

UPD: There will be 8 problems. There will be only be an interactive problem if the Collatz Conjecture is true...

UPD: Thanks to everyone who participated! I hoped you enjoyed thinking over the problemset. The editorial is available, complete with solution code and hints. Special congratulations to the winners.

2 kk19212 7 (339)
3 xyf007 7 (341)
4 Tyyyyyy 7 (345)
5 F1aMiR3 7 (345)

• +538

By Agnimandur, 9 months ago,

Hello Codeforces!

Coaching

I am a USACO Platinum contestant, former Codeforces International Master rated 2377, Leetcode 2600, member of the Binarysearch.com contest team, and author of Codeforces Round #736 (Div. 1) and Codeforces Round #736 (Div. 2). I'm offering one on one competitive programming lessons OR leetcode practice, online over Zoom.

• I can help you with Leetcode.com and Binarysearch.com problems. I can help explain common interview programming techniques.

The price is $50 an hour due to exceptionally high demand. Interest If you're interested, please send a direct message to Agnimandur over Codeforces! Alternatively, send a direct message over Discord to Agnimandur#9256. Frequently Asked Questions Suggest more questions in the comments and I'll respond to them up here! 1. What's your coaching method and why do you think it will help in a problem solving? My coaching ideology is simple: the only way to improve is to practice. You have to be willing to put in the time and energy to practice. I come in by helping guide your practice: I can point out common ideas, so that you can look out for them in later problems. I can discuss coding details, so that you can solve problems faster later. And I can hopefully instill in you the confidence to solve harder problems, without giving up or looking at editorial. 2. Why do you think people have to pay you instead of, for example, solving random problems? In what your lessons better than practicing independently and why does it worth$20 per hour? You can solve random problems if you'd like. I only offer my services as an option, if you feel like you need more direction and mentorship. $20 is a reasonable market rate. 3. Do you understand that gaining mathematical thinking skill (if you don't have it form birth, that is true for 99%) is hard and long process that require many years? And no coach can significantly speed up this process. Nevertheless, this skill is crucial for problem solving. Tell the truth to people, how long will they need to take lessons from you and, therefore, pay you, to reach at least 2000 rating? Absolutely, problem solving skill is something no coach can "teach" you. What coaches can do is hone that skill. Everyone can solve difficult problems if they have the encouragement, willpower, and time to solve them. Many hours of practice will make the difference, not just one coach. Do not expect a miracle improvement to 2000 if you don't want to put in many hours of your own time. 4. I know that people from top 100 (I won't say who exactly, just dm some youtubers) are ready to give lessons for even cheaper, why not to take lessons from more skilled experienced people for less cost? Perhaps, but are these classes 1 on 1? I know Errichto does group lessons. 5. Will there be a free evaluation session? Yes! UPDATE: Price increased to$35/hr due to demand.

• +212

By Agnimandur, 10 months ago,

All the division 2 problems were created by Agnimandur. 1548E - Gregor and the Two Painters was created by Benq. I hope that this hint-based editorial helps you, no matter what your rating is! Solution code is provided in both C++, Java, and Kotlin when available.

Hint 1
Solution

Hint 1
Hint 2
Solution

Hint 1
Hint 2
Hint 3
Hint 4
Solution

Hint 1
Hint 2
Solution

Hint 1
Hint 2
Hint 3
Solution

Hint 1
Hint 2
Hint 3
Solution

Hint 1
Hint 2
Hint 3
Hint 4
Solution

Hint 1
Hint 2
Hint 3
Hint 4
Solution

Hint 1
Hint 2
Hint 3
Hint 4
Hint 5
Solution

1548E - Gregor and the Two Painters

Hint 1
Hint 2
Solution

• +73

By Agnimandur, 10 months ago,

Hello, Westeros!

I'm glad to invite you to Codeforces Round #736 (Div. 1) and Codeforces Round #736 (Div. 2), which will be held on Aug/01/2021 17:35 (Moscow time).

The round will be rated for both divisions. Each division will have 5-7 problems and 2 hours and 15 minutes to solve them. There will not be an interactive problem, so yay!!!

This round would not have been possible without the following individuals:

1. Aleks5d, for awesome coordination of my round.
2. Benq, for extensive testing and contributions throughout the round, especially for 1548E - Gregor and the Two Painters.
3. Monogon, for discussing problems and statements with me for hours on Discord.
4. amgfrthsp, for translating statements into Russian.
5. MikeMirzayanov, for Codeforces and Polygon.

32 testers

The round had a total of 32 testers. I tried to get a "rainbow" of testers to help guarantee a most balanced round. Thank to you to each and every one of them!

This is my first round ever written, and I sincerely hope you enjoy it, regardless of your rating!

Score Distribution

Div 1: 500 — 1000 — 1750 — (2000 — 1000) — 3500

Div 2: 500 — 750 — 1250 — 2000 — 2500 — (2000 — 1500)

Winners

Congratulations to all our winners in the round!

Div1

1. slime, congratulations on the AK!
2. tourist, congratulations on the AK!
3. yhx-12243
4. heno239
5. Isonan

Special congratulations to antontrygubO_o and Subconscious for definitely reaching the rank of Legendary Grandmaster!

Fastest Solves

• +1253

By Agnimandur, history, 15 months ago,

Hi Codeforces,

Many of you know about the CSES Problem Set, an online collection of over 300 competitive programming problems made by pllk! I have decided to clone all the CSES problems onto Codeforces! Each CSES category will be its own separate gym contest, listed below.

• Introductory Problems (19 problems)
• Sorting and Searching (35 problems)
• Dynamic Programming (19 problems)
• Graph Algorithms (36 problems)
• Range Queries (19 problems)
• Tree Algorithms (16 problems)
• Mathematics (31 problems)
• String Algorithms (17 problems)
• Geometry (7 problems)
• Additional Problems I (38 problems)
• Additional Problems II (39 problems)

There are two main reasons why I decided to do this project.

Slow CSES Judge

The CSES Judge is very slow, often resulting in correct solutions that should get accepted instead getting the TLE verdict. This is especially a problem for programmers who use Java. However, the Codeforces judge is much faster, which solves this issue.

Codeforces API

The Codeforces API is quite powerful. By adding these problems to gym contests, these problems can now be accessed by the Codeforces API, which will aid developers and people who use Codeforces bots to suggest problems.

Note: Work in Progress!!

This is still a work in progress! There are over 300 problems on CSES, and it will likely take me months to get them all on Codeforces. Therefore, I recommend you "favorite" this blog post, and check back on the contests regularly.

• +41

By Agnimandur, history, 15 months ago,

This is my current rating. As you can see, it says I am rated 2113. However, it also says I am a "Candidate Master", and my color is still purple!

This is my most recent contest. There are several things wrong with it.

• Its an educational round (rated for people <2100). If I was over 2100, why would it appeared in the list of my rated contests!

• The rating change listed was "0".

• Even though there was no rating change, we still see that my color changes from yellow to purple on the right!

MikeMirzayanov please take a look at this! This is probably an issue for many other people too.

• +118

By Agnimandur, history, 15 months ago,

Do You Want to Go to College? Are You Good At Writing Codeforces Rounds?

If so, then read on ahead! You will learn how quick and easy it is to go to college with the help of Codeforces!

College is Expensive.

The cost of MIT, a prestigious American university, is 53,790 USD per year. Even though scholarship is usually available, the average American student ends college with 37,000 USD in student debt! [Source] Student loan is also very pricey, with the average loan charging 5.8% interest per year. [Source]

However, Codeforces pays its problem setters big money! For a combined, Div 1+2 round, you can earn an average of approximately 400 USD. [Source]

Time Breakdown To Make a Round

Per Problem:

• 5hr to create idea, propose statement and solution, discuss with coordinator

• 1hr to write and revise statement, pictures, notes section

• 1hr to write and revise tutorial

• 1hr to write validator, checker, validator tests, checker tests

• 2hr to write model, alternative, and fake solutions

• 3hr to write generators for actually good test cases

• 2hr to make unexpected edits, changes from tester feedback

Per Contest:

• 8 problems per div1+div2 round.

• 50hr to come up with problem ideas that get rejected by coordinator.

• 30hr to discuss feedback with testers and coordinator, create announcement, editorial blog, answer clarifications during round, and any miscellaneous work.

Total Time To Write a Complete Round: 200 hours Assuming you work full time just problem setting (40 hours a week, 50 weeks a year), you should be able to write 10 high quality rounds a year!

Yearly Profit From Writing Codeforces Rounds: 4000 USD

How long will it take to pay off your student loan? Well, just run this quick python program to find out!

debt = 37000
year = 0
while debt > 0:
interest = 0.058*debt
debt -= (4000-interest)
year += 1
print(year) #we get an answer of 14!


Conclusion: It Will Take 14 Years to Pay Off Student Loan Debt Via Codeforces

This of course assumes that you don't have to pay any other expenses, and problemset as a full time job. On the bright side, imagine what your rating would be after those 14 years...

Warning: This is satire. Please don't actually write 140 Codeforces rounds to pay for college. Unless you want top contributor spot.

• +216

By Agnimandur, history, 17 months ago,

Hello Codeforces!

What is Reaper?

Reaper is a math game all about timing, strategy, and patience. It was developed by folks at AOPs, and many games have been played on that site. How Reaper works is that whenever you reap, you get points equal to the current time and the time of the last person to reap. Additionally, there is a cooldown between reaps. Thus, the strategy is deciding when to reap. If you wait too long someone else might reap and you won't get your points. If you reap too quickly, you will get very few points which is very inefficient, due to the cooldown. Thus, you need to find the optimal time to reap, and also finetune your reaping strategy based on your opponents.

Standard versus Blitz Reaper

Standard Reaper usually has a long reap cooldown, usually in the range of several hours to a day. Thus, these games usually take days or weeks to finish, and require patience. Usually, standard reaper games have dozens or even hundreds of competitors! Blitz games are very different. They have very short reap cooldowns, usually around 10 seconds. Blitz games usually are very quick to finish, so players are recommended to continuously play from beginning to end! Although strategy is important in both modes, in Blitz reaper keeping track of your opponent's reap cooldowns is critical to success! Of course, the Red Crab Inn has complete support for both modes!

Inviting the Bot To YOUR Server

Setting up the bot is easy. Simply add the bot to a Discord server in which you are an administrator using the link above. Then, in any channel, simply type in \$reaper. This will automatically create all the channels and roles the bot needs to function! That's it! You're done setting up the bot, and you can immediately move on to starting your first game!

Help

The Red Crab Inn bot supports many commands for optimal gameplay ease. At any point if you need help, simply type in help into the #reaper channel (created by the bot) to pop up the help menu. Of course, if you have any questions, concerns, or other queries please please direct message me on either Discord or Codeforces!

Source

All Reaper game code was written by me in Python, using the discord.py library, and hosted on repl.it. The idea for the game of Reaper is taken from AOPs. Check out the public github repository for more! If you find Reaper interesting, please share the bot with your friends!

Public Server

If you want to play on the Reaper Public Server, maintained by myself, click the above link.

• +23

By Agnimandur, history, 18 months ago,

Monogon's pleas for contribution have finally worked! As of Global Round 12, Monogon now has 205 contribution, beating Errichto's 204 contribution. Mike Mirzayanov of course doesn't count.

Let us celebrate Monogon's special day!

• -57

By Agnimandur, history, 2 years ago,

So, I noticed that there is a selection for the targeted division of a proposed Contest.

However, there is no way to propose a Div 3 round. How do you propose a Div3 round?