Codeforces Round # 640 (Div. 4)

Revision en1, by MikeMirzayanov, 2020-05-07 19:54:33

Hello Codeforces!

Yes, it is not a mistake I decided to run the first Div. 4 round!

I want to be absolutely, completely sure that everything works as it should before the start of a Div.1 / Div.2 round. So I decided to do such an experiment. Since I am the writer of all problems in the round, in any case, no writer will suffer during the experiment.

As you noticed, recently the number of participants has increased dramatically. On the one hand, the number of gray and green participants in total exceeds the number of other participants. On the other hand in typical div.2 rounds, gray and green participants rarely can solve more than 2 problems. I remember that when I myself participated in the competitions, then every solved problem pleased and motivated (hello, endorphins!)

As an experiment, I plan to hold the first round for participants with ratings up to 1400. The format of the event will be identical to Div. 3 rounds:

  • 5-7 tasks;
  • ICPC rules with a penalty of 10 minutes for an incorrect submission;
  • 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
  • after the end of the open hacking phase, all solutions will be tested on the updated set of tests and the ratings recalculated
  • by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400).

I urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism, but simply to take part unofficially. Please do not spoil the contest to the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating with unsporting behavior. To qualify as a trusted participants of the fourth division, you must:

  • take part in at least two rated rounds (and solve at least one problem in each of them),
  • do not have a point of 1600 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1400, then the round will be rated for you.

Since such rounds do not imply the presence of strong knowledge and skills, most problems will be on topics: simple mathematics, implementation, greedy, sortings, constructives. I think simple binary search applications, the very easy applications of dynamic programming or graphs can be also used. I believe that in such a round the problems on "strength of hands" are more appropriate, where you just need to write (sometimes optimally) some process: the purpose of such rounds is also to help improve the programming technique. Almost all problems (or even all) will contain multiple test cases — this will prevent the occurrence of a queue, simplify the preparation of tests. Yes, first of all, the goal of this round is for beginners. For this reason, I would not be surprised if some ideas of the problems are not new. The plan is to make the preparation of such rounds simple and reliable, and at the end to have interesting and useful problems for beginners.

I am the writer of the first Div.4 round. We are just starting, so the complexity of the problems may deviate somewhere from your or my expectations. Wait and see.

Later I will add to the post a list of testers. And the first "thank you" is sent to antontrygubO_o, who helped with the review and selection of problems.

I hope you enjoy the problems, and the round will be interesting!

Tags div4, codeforces


  Rev. Lang. By When Δ Comment
en11 English MikeMirzayanov 2020-05-09 23:12:08 6 Tiny change: 'ds:\n\n* I don't afraid o' -> 'ds:\n\n* I'm not afraid o'
en10 English MikeMirzayanov 2020-05-09 15:36:21 0 (published)
en9 English MikeMirzayanov 2020-05-09 15:35:56 6420 (saved to drafts)
en8 English MikeMirzayanov 2020-05-09 13:12:02 27 Tiny change: '020-05-08].\n\n' -> '020-05-08],\n[user:bfs.07].\n\n'
en7 English MikeMirzayanov 2020-05-08 18:55:14 320
en6 English MikeMirzayanov 2020-05-07 21:54:51 71
en5 English MikeMirzayanov 2020-05-07 20:16:34 7 Tiny change: 'nt of the third division<' -> 'nt of the fourth division<'
en4 English MikeMirzayanov 2020-05-07 19:58:06 242
en3 English MikeMirzayanov 2020-05-07 19:57:05 2 Tiny change: 's:\n\n* 5-7 tasks;\n*' -> 's:\n\n* 5-8 tasks;\n*'
en2 English MikeMirzayanov 2020-05-07 19:55:55 50
en1 English MikeMirzayanov 2020-05-07 19:54:33 3619 Initial revision (published)