Hi, Codeforces! After the recent round I am sure that many people want to orz author of this round, McDic. However, people may not know reasons why to orz him, so I want to provide TOP 10 REASONS TO ORZ McDic!

1. McDic is Korean! McDic orz
2. McDic's announcement of Round #589 is the highest upvoted Div2 only round announcement in the Codeforces history! McDic orz
3. This announcement is also the highest upvoted round of $$$2019$$$ after Hello 2019! McDic orz
4. Editorial of the round was prepared early and published right after the contest. McDic orz
5. McDic learns from his own mistakes rather than step into them again and again. His recent round has clear statements, perfect difficulty gaps and strong pretests! McDic orz
6. Problems created by McDic are very exciting! Less coding, more thinking, exactly what Codeforces needs! McDic orz
7. Before the round, McDic wrote Python solutions for all problems to ensure they fit in TL. Not many problemsetters on Codeforces care about Python, but McDic does! McDic orz
8. McDic really cared about testing his round. He divided it into $$$2$$$ testing phases, and his round has $$$12$$$ testers in total! Everything to make sure that the round will make Codeforces users happy! McDic orz
9. McDic will come back with a Div1 round in future! McDic orz
10. McDic didn't pay me to write this blog. McDic orz

If I don't become the international grandmaster before the new year, I’ll dye my hair cyan (according to my true level) for a week.

I just got a bit confused:

Numbers of registered users to last $$$3$$$ Div1 + Div2 combined contests: $$$12129$$$, $$$10160$$$, $$$8335$$$

Numbers of registered users to last $$$3$$$ Div2 only contests: $$$12266$$$, $$$11063$$$, $$$9832$$$.

BUT

Numbers of registered users to last $$$3$$$ Div3 contests: $$$13785$$$, $$$13216$$$, $$$12619$$$.

Of course, the time when the contest is held matters a lot, but still. Why do Div3 contests regularly gather so much more participants than Div2 and combined rounds? Div3 are rated for far fewer users than Div2 and combined rounds. Do low-rated coders avoid Div2 just because their problems just seem too hard?

Hello again, Codeforces!

I am glad to invite you to Codeforces Round 580, which will take place on Aug/18/2019 16:45 (Moscow time). Round will be rated for both divisions.

All problems in this round were created and prepared by me, antontrygubO_o. I tried to make them interesting and hope that you will enjoy them!

A lot of thanks to arsijo for the excellent coordination of the round, kefaa2, gepardo, danya.smelskiy, re_eVVorld, Xellos, GandalfTheGrey, prof.PVH, KAN for the testing and valuable comments, and to Mike MikeMirzayanov Mirzayanov for the amazing platforms Codeforces и Polygon.

Participants in each division will be offered 6 problems and 2 hours 10 minutes to solve them. As usual, I strongly recommend reading statements of all problems!

I wish you good luck and high rating!

UPD1:

Scoring distribution of Div $$$2$$$ round: 500 — 1000 — 1500 — 1750 — 2250 — 3000

Scoring distribution of Div $$$1$$$ round: 500 — 750 — 1250 — 2000 — 2500 — 3000

UPD2:Editorial

UPD3 Congrats to winners!

Div 1:

1. TLE

2. Um_nik

3. mnbvmar

4. Benq

5. CauchySheep

Div 2:

1. kkkkk11

2. sucuk

3. ujrepacul

4. zzffxx

5. Illicit

Suppose than person A comes up with an interesting task, but is not able to solve it. Then, A sends this problem to his friend B and asks for help in solving it. After B successfully does that, the question appears: whose problem is that, A's or B's?

I don't like the approach when A is considered an author as in that case he can, for example, just spam B with tons of statements he just came up with without any intuition if those are solvable, and that doesn't sound as highly intellectual work. From the other hand, I don't like approach when B is considered the author too: he is doing the same amount of job as any contestant would do during the contest. A more interesting example: if A sends his problem to both B and C and they solve it with a difference of 5 minutes. Would be weird to say they both are coauthors, would be weird to say that the first one who solved is author either.

To avoid confusion, I just prefer not to share my unsolved problems with anyone, but in this case, some interesting problems may be lost. What are your thoughts on this question?

Hello, Codeforces!

We are glad to invite you to the Codeforces Round #572, which will be held on Friday, 5 July at 18:05. The round will be rated for both divisions (as this time we thanked MikeMirzayanov).

Round was prepared by us, antontrygubO_o and kefaa2. This is our first round, and, as we hope, not the last one!

A lot of thanks to arsijo for the excellent coordination of the round, gepardo, GandalfTheGrey, progmatic2, zoomswk, ecnerwala, AllCatsAreBeautiful, DmitryGrigorev, Markellonchik, dasfex, Taran_1407, slicedclementines, DenisPushkin, austrian_artist, mmello, sas4eka for the testing and valuable comments, and to Mike MikeMirzayanov Mirzayanov for the amazing platforms Codeforces и Polygon. (please rated)

Participants in each division will be offered 6 problems and 2 hours to solve them. We strongly recommend reading statements of all problems! The scoring distribution will hopefully be announced before the round begins.

We wish you good luck and high rating!

UPD1: Shortly after the contest, we'll be on the community Discord server to discuss the tasks.

UPD2: Slight corrections: participants in Div $$$1$$$ will be offered $$$5$$$ problems, one of which will have $$$2$$$ subtasks, while participants in Div $$$2$$$ will be offered $$$6$$$ problems, one of which will have $$$2$$$ subtasks. Please note that subtasks will be unusual this time and will differ not only by constraints.

UPD3:

Scoring distribution of Div $$$2$$$ round: 500 — 1000 — 1250 — (500 + 1250) — 2250 — 2750

Scoring distribution of Div $$$1$$$ round: (250 + 750) — 1250 — 1750 — 2250 — 2500

UPD4: Editorial

UPD5 Congrats to winners!

Div 1:

1. Um_nik

2. ugly2333

3. Radewoosh

4. Marcin_smu

5. Endagorion

Div 2:

1. esbee

2. handsomeIvan

3. philologist

4. teamskiy

5. NeoGul

Close to New Year, I think, a lot of competitive programmers were setting their goals for the year 2019. Some posted their goals, some not, but most of them were related to their rating ambitions (like becoming IGM by end of 2019). I think that the ACM ICPC final 2019 is a good day for setting the goals for ACM ICPC season 2019-2020.

I know that studying and training is a much more productive way of getting closer to your goals than dreaming and talking, but I feel like reading which goals other participants set for them may be really motivating and inspiring.

Feel free to share your goals with the community, no matter if you are a disappointed participant from this year final or a student of a university which has never been to final before!

Yesterday I saw the announcement of the contest Code Mutants on Codeforces, it said contest will take place today (19th February). I went through the announcement, it said:

"Top 3 contestants will be rewarded with 250 Laddus!! from CodeChef.Some of the top contestants will be selected for onsite round where prizes worth 10,000 INR are waiting for you!!"

I thought: "Cool! I definitely should try it, I feel inspired!"

So I felt inspired and went to the CodeChef. In announcement there, I saw the following:

Hoping to get to onsite, I filled in this form!

Then, the contest started. Tasks turned out to be very interesting! Even more impressive was innovative Tex formatting:

After I solved the first task, I tried to submit it and clicked Submit. However, it was testing too long. "Maybe it's TL?" — I asked myself. After it was testing for 5 more minutes, I dropped that idea.

That was kinda strange. I went to my submissions of that problem and discovered that I had no submission for it. Moreover, after I tried to send the solution 5 more times, I still had no submission for it. However, after I got too nervous, I got the following message from Codechef:

So it was receiving my submissions, just wasn't displaying them anywhere. Still happy about the great contest, I went to the contest page and saw that tasks were so hard that nobody managed to solve a single problem!

However, it turned out that some solutions still were tested, though not displayed there. I went to the scoreboard and saw that somebody managed to submit a few problems. However, there were some cheaters, who, as their penalty indicates, submitted problems even before the contest started.

It got really suspicious. I went to the announcements, expecting to see the message telling about technical issues, but here is what I saw:

Nice! That's exactly what would help me now.

However, later they acknowledged that they experience some technical issues:

Anyway, I really enjoyed the contest! I have never laughed so much during the actual online competition. Tell about the contests that you enjoyed!

Thanks for attention

P.S. I didn't want to imply anything bad about the problem setters or to express any disrespect to organisers: they still have done a lot of work. Just wanted to share the best contest of my life impressions!

After 6 months without contests, CsAcademy is finally back!

https://csacademy.com/contest/fii-code-2019-round-1

I am just curious.

Suppose some problem has a randomized solution which fails with probability at most . If it has, say, 100 tests, the probability of failing some of them is about . Therefore, once in 10⁴ it may happen that correct randomized solution doesn't pass.

Has anyone experienced anything like that? Maybe even the exact solution that didn't pass got AC after submitting it the second time? Or am I getting something wrong?