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anveshi's blog

101 Hack 53 — HackerRank
By anveshi, 6 years ago, In English

Hello Codeforces community,

I would like to invite you to join HackerRank's 101 Hack 53 which will start at 1500 UTC, March 2, 2018.

There will be five tasks and three hours for you to solve them. The contest will be rated and the top ten contestants will receive HackerRank T-shirts! The problems are prepared by jugnu and me and tested by kevinsogo and qoo2p5. I hope you'll find the problemset to be interesting.

I would like to thank kevinsogo for his assistance in the preparation of the contest and an excellent platform polygon, which greatly simplifies the preparation of the problems.

I suggest you to read all the problems since there are subtasks and partial scoring.

Happy Coding & H A P P Y - H O L I !

Update-1: The contest starts in 1 hour and 30 minutes. Good luck to everyone :)

Update-2: Contest is over and Editorial is up. Thanks to all the participants. Congratulations to uwi for being only one to solve all the problems completely that too within 2hrs.

Apologies for slightly harder B and C. Feedback about the problem set is welcome:)

Congratulations to the winners. Here is Top 10
  • Vote: I like it
  • +88
  • Vote: I do not like it

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6 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

Is it a coincidence, or most of the problems seem like a "chess"-based problem :)

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    6 years ago, # ^ |
      Vote: I like it +13 Vote: I do not like it

    I would say it was a coincidence that three of the problems involved 2D grid. Thanks for participating and congratulations for doing well.

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6 years ago, # |
← Rev. 2   Vote: I like it +16 Vote: I do not like it

I spend the last minutes of the contest trying to get 1,5 pts. 15 instead of 13,5 on the last task. Finally I figured out the issue with calling 1e6 times gcd and replaced it with some sort of Erathostenes sieve but I was late by a minute. It costed me 2 places — still not the first 10 but maybe, if some participants were not eligible for prizes ... :)

And I liked the problemset.

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6 years ago, # |
  Vote: I like it +2 Vote: I do not like it

D is more easy than B & C..

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    6 years ago, # ^ |
      Vote: I like it -22 Vote: I do not like it

    The only thing hard about the problems, is their editorial. When I read B editorial, I thought it was too complicated, then I scroll down and see tester's code, and it's the same as my idea. Similarly C is pretty easy. D is a standard DP problem. I regret not knowing about the contest before hand. Easy ratings.

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      6 years ago, # ^ |
        Vote: I like it +26 Vote: I do not like it

      You can say that about every contest. Let me remind you some anegdote:

      "Christopher Columbus, sick and tired of having to listen that if he had not discovered America, someone else would have done it, asked the following question. Put the egg in the vertical position on the table. Obviously nobody was able to solve it. He took an egg, smashed it's bottom part and placed the egg on the flat surface. Now, once you saw the solution, everybody can do that again. The trick is to do this first."

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6 years ago, # |
← Rev. 2   Vote: I like it -10 Vote: I do not like it

Simple idea for B : If the sum is not even, then it's trivial to see that you can't tile with 2x1 dominoes. So, either the two rectangles we get are even-even or odd-odd. If it's odd-odd, then no solution is possible, because when we are tiling a rectangle of odd area, we can leave exactly 1 square untiled on one edge. This square can only be at an odd position.

eg: when tiling 5x5 area with 2x1 tile, the only positions you can leave uncovered are (1,1),(3,1),(5,1). But the second area is shifted by 1 unit, which means it's odd squares on the edge will never coincide with the other area's odd squares. Hence, These vacant 1x1 squares can not be tiled.

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6 years ago, # |
← Rev. 2   Vote: I like it +68 Vote: I do not like it

I liked the contest very much.But I have a complaint(or a suggestion) for Hackerrank.
During the contest its distracting to recieve messages like
1.Please send me code for .... problem
2. Please give me a small hint for ... problem
3. Please help me debug my code and putting the code in message.
4.Please say which category does this problem fall into and giving several options for the tags.

I have received around 7-8 messages per contest for last 3 contests.So,I dont know how people at top regularly tolerate such behaviour during contests.

My Solution:
I would like to know if its possible to disable notifications(or messages) for messages recieved during the contest (or permanently) on Hackerrank.

Sad part: I am sad that majority(atleast 80%) people who sent such messages are Indians.I hope these people realise it doesnt work that way during a contest.

On a lighter note,even follow notifications during contest are not good because I expect a correction in a question on seeing a notification

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    6 years ago, # ^ |
      Vote: I like it +6 Vote: I do not like it

    I've heard that some schools/universities(?) are taking performance on different platforms into account. I generally consider this a very bad practice, as it causes a lot of teamwork + cheating in different contests.

    I can't imagine another reason for cheating, because if you just would like to get a better rating for yourself, then you would be cheating yourself — it is not funny.

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I have always thought that it takes a long time for CF to update ratings ^_^.

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