By ItsNear, history, 5 days ago, In English,

UPD note that the score distribution has changed

UPD2: LHiC found a bug in the author solution of div1-F. We are working on the situation.

UPD3: we found a correct solution for div1-F and both submissions made during the contest pass all the tests against the correct solution. The round remains rated.

Hi, everybody,

Codeforces round 488 for both divisions will take place on Jun/16/2018 19:35 (Moscow time). The round will be 2.5 hours long (which is 30 minutes longer than usual).

The contest is created by NEAR and its friends. NEAR is working on teaching machines to compete in programming competitions. Read our blog post to learn more about the state of the art in the program synthesis today, our vision, and how you can help us bring this vision to reality.

The contest will feature 6 problems for each division, with 4 problems shared across them.

The problems for the contest are from the test rounds hosted on a system JavaBlitz last year. If you participated in any of the JavaBlitz rounds, you shall not participate in this round.

The score distribution in the first division is 500-1000-1000-1500-2250-3000

In the second -- 500-1000-1500-2000-2000-2500

The round is rated for both divisions.

All problems are initially created by myself, Alexander "ItsNear" Skidanov, and by Nikita "neckbosov" Bosov. David "pieguy" Stolp, Alexander "AlexFetisov" Fetisko, Marcelo "MarX" Fornet, Nikolay "KAN" Kalinin and Mikhail "cerealguy" Kever helped tremendously ensuring the high quality of the problems.

As a closing note, we are constantly looking for people to help us label competitive programming data for research. Read more here.

Congratulations to winners!

Div. 1:

  1. Um_nik
  2. Errichto
  3. scott_wu
  4. Reyna
  5. matthew99

Div. 2:

  1. FiveAtomTree
  2. shayan.p
  3. gauss148
  4. kessido
  5. codejudge

The editorial is published here. Thanks for your participation!

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By ItsNear, history, 28 hours ago, In English,
Tutorial is loading...
Tutorial is loading...
Tutorial is loading...
Tutorial is loading...
Tutorial is loading...
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Tutorial is loading...
Tutorial is loading...

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By DmitryGrigorev, history, 11 hours ago, translation, In English,

Hi, Codeforces! I'm glad to invite everybody to the #489 Codeforces Round, which will be held as soon as tomorrow, on Monday, June 18, 2018 at 19:35. The round will be rated for all participants from the second division. As usually, we will be glad to see participants from the first division out of competition!

Problems for the round have been invented and prepared by us, pupils of Moscow school №2007, Dmitry DmitryGrigorev Grigorev and Fedor ushakov.fedor Ushakov. We want to give thanks to Andrew GreenGrape Raiskiy for his aid in preparing and testing of the problems, to Ildar 300iq Gainullin who has tested our problems too and to the coordinator Nikolay KAN Kalinin, since our sometimes strange and undeveloped ideas have become eventually the Codeforces round. Also, we say thank you to Mike MikeMirzayanov Mirzayanov for his unbelievable Codeforces and Polygon platforms.

You will receive 5 problems and 2 hours for solving it. During the round you will be helping for an extraordinary girl Nastya, who has been living in Byteland and sometimes receives very strange gifts for her birthday :).

Score distribution will be announced, traditionally, closer to the start of the contest.

We're holding our the first and, I hope, not the last round in Codeforces, so I hope a lot you will like our problems. Please, read all the problems. Anyway, I wish luck and high rating for all the participants!

I'm looking forward your participation.

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By teja349, history, 18 hours ago, In English,

Recently I participated and got Rank 2 in Quick Code conducted by NSIT on Codechef. In the poster, they have mentioned prizes worth 25K (hopefully INR). On Codechef, they mentioned Cash prizes worth 25K.

I was excited that the prize money would be somewhere between (5K to 10K) in cash for Rank 2.But yesterday,I have mail that it was prize coupon from Codechef worth 500 and some coupon code attached(Maybe for CCDSAP).

I knew the person who got Rank 1.He has received some coupon which was expected to expire in next 8 hours from the time of receival.Later he negotiated it to 200 Codechef Laddus(a great deal I guess).

I have contacted them regarding website saying it as Cash prizes.But they were like prizes which are worth that cash.I dont know how 200 Laddus + 500 INR coupon + maybe some more prizes for ranks after 2 = 25K.

Its not that I am unhappy with the contest(The problems were okayish).Since it is a university contest, I believe there must have been funds worth 25K allocated by the management.Also NSIT is considered to be among good institutes in India.Hence, this was not expected from them.

Also people might feel, it is bad to post this way.But I think it should be addressed in public because there was no intent from their side when I called them.Also I feel Codechef takes a lot of care regarding many other aspects of external contest. Maybe its time for them to take care of this part too after the contest.Because it adds to their reputation at the end of the day.I want to make it clear that I understand it is not responsibility of Codechef.

Coming back to the Title of blog post

I do not think I will use that coupon.So I thought I will give it to a random person. Hence I created this form.I will message the 10th distinct handle who fills this form with the details of the coupon code.

PS: I have also not received some shirts from Hackerrank yet from long back(atleast 3 months old).So does anyone know how to contact them regarding this.

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By AmrMorsy2, history, 7 hours ago, In English,

So the problem state that " if one square is completely inside another, they intersect. If the two squares only share one common point, they are also considered to intersect. "

Yet this code gets AC and all it does try each pair of points and check if it intersect with the any other line in the second square so in total there are 4 lines of the sides and 2 for the diagonals.

Yet you can have a square totally inside the other without any of the 6 lines intersect the second square as in this

0 0 100 0 100 100 0 100 1 53 3 51 5 53 3 55

The answer should be yes yet the AC code gets no. I'm not sure if there's a wrong case tho or just weak ones.

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By killer_god, history, 9 hours ago, In English,

On 23rd june codeforces round is colliding with a rated contest in codechef. On 30th june again another codeforces contest is colliding with codechef lunchtime. Is it possible that the timings might be slightly changed that they don't collide? I'm sure many participants would like to give both contests and don't want to choose between the 2 especially since it is summer vacation and everybody has lot of free time.

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By alessandrosolbiati, history, 6 hours ago, In English,


n = int(input())
a = sorted((input() for _ in range(n)), key=lambda x: len(x))
v = all(a[i] in a[i+1] for i in range(n-1))
print('YES\n'+"\n".join(a) if v else 'NO')


R = lambda: (int, input().split())
n, a, b = R(), R(), R()
print(' '.join(map(str, (x for x in a if x in b))))


R = lambda: map(int, input().split())
n, k = R(), 
v, t = [], [0]*n
for p, c, i in sorted(zip(R(), R(), range(n))):
    t[i] = sum(v)+c
    v += [c]
    v = sorted(v)[::-1]
    if len(v) > k:
print(' '.join(map(str, t)))

*find more here

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By E869120, history, 5 days ago, In English,

Hello everybody!

I'm delighted to invite you to anniversary round AtCoder Beginner Contest 100, which starts at Saturday, June 16, 2018 at 21:00 JST. The time is as usual as previous round. (However, some of AtCoder contest start time is unusual...)

This is the fifth round for a Japanese twin-brothers: E869120 and square1001. I already held AtCoder Beginner Contest 064, 076, 088, 096, and this time, it's 100. Multiple-of-four again, again and again! (Where is the probability 1/1024 ???) Anyway, ultimate thanks for rng_58 for reviewed and refined my problems, chokudai for creating one of the best contest platform in the universe. It is obvious that I could not be able to host the contest without cooperation of these two people.

The round is rated for participants whose rating is strictly lower than 1200. High-skilled participants whose rating is >=1200 is also welcomed to participate as out of competition (unrated).

Scoring is 100 — 200 — 300 — 400, as usual. The contest duration is 100 minutes.

Let's participate in the contest, good luck and high rating! Also, hope to have a ultimate-great memory in the first 3-digit round!

Finally, AtCoder managed to hold the contest which the first-digit is not '0'. Since this contest is the 100th anniversary round, so some problem can be associated with anniversary. Wish AtCoder and other contest platforms will be continue till 4-digit round :)


1. Judge queue is clogging now.
2. Now, judge queue is fixed. Sorry for inconvenience.
3. Editorial Uploaded.

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By wallcrawler, history, 9 hours ago, In English,

Not sure if it'll help everyone, as many of you would be knowing these things....but here is a link for a good blog I found on the internet :

Get Started With The Sport Of Competitive Programming

And a curated list of awesome Competitive Programming, Algorithm and Data Structure resources, which can be found on :

List of algos, tutorials on language used also data structure, problem resources etc..

The latter has a list of problem classifiers which I found really helpful :) Thought to share with you all.. Kudos!! Happy Coding!!

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By sankalp_, history, 10 days ago, In English,

Dear all,

I am not good at competitive programming but I am willing to put in the effort to get better at it. I had a small question which I though might help me and a lot of people like me who want to get better at CP.

It is not a question asking how to solve problem X or which method to use. I just wanted to know if, let's say you start solving a question. Can you look at the question and realize.. Oh!! this question can be solved using DP or graphs or some paradigm Y.

Or rather, how long does it usually take for the idea to click in your head?

Also, do you have a specific method to determine what to use(I know it is not possible in most cases) like looking at the constraints or the time limit or anything like that?

Is there any particular pattern you follow while solving problems? Like.. do you select a problem to solve in you free time randomly or based on a particular tag?

I found a couple of good blog entries by Morass and DarthPrince from which I practice topic specific problems and I am practicing algorithms from CLRS. Are there any resources that I am missing? If so can you please specify the names or post the links?

Also, on an average basis, how much time do you spend on CP per day?

Thank you.

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