mohammedehab2002's blog

By mohammedehab2002, 4 years ago, In English

We invite you to participate in the CodeChef October Lunchtime — the 3-hour contest which offers 5 challenging problems to be solved, next Saturday, October 31st, 19:30 to 22:30 IST.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

The members of the problem setting panel are:

Prizes: The top 10 Indian and top 10 Global school students from ranklist will receive certificates and CodeChef laddus, with which they can claim cool CodeChef goodies. Know more here.

Video Editorials: You will now also be able to solve your doubts with the help of our amazing educators and their helpful video editorials. Don't forget to check out our YouTube Channel soon after the contest ends. Hit the Subscribe button so you don’t miss out on any video editorials in the future.

Good luck and have fun!

UPD: Thanks everyone for participating! Here are some quick solution sketches. You can find more detailed editorials on CodeChef.

ANDOR
SUBMEXS
GSUB
COPAR
SSO
CDSUMS
EFLIP
  • Vote: I like it
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4 years ago, # |
  Vote: I like it +8 Vote: I do not like it

Hope the timing doesn't get changed like the last codechef Lunchtime

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4 years ago, # |
  Vote: I like it +38 Vote: I do not like it

Congrats on reaching red!

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4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

XOR missiles on their way, btw congrats on reaching red

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

Problem's arranged in sorted order of difficulty ?

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4 years ago, # |
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Attending lunchtime contest in dinner time :D

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4 years ago, # |
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How to solve Chef Likes Good Sequence ??
Have there any way to solve only subtask.1 for Q=1 ??? I tried but failed.

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    4 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    You are looking for a subsequence not a subarray.

    HINT: It can be done greedily.

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      4 years ago, # ^ |
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      Thank you sir..subsequence not a subarray its solved the problem <3

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

The video editorials to the problems are uploaded on Youtube

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4 years ago, # |
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Can COPAR be solved using binary search?

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    4 years ago, # ^ |
    Rev. 3   Vote: I like it 0 Vote: I do not like it

    I tried but got WA Submission

    Test Case
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    4 years ago, # ^ |
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    I don't think it's possible.

    My reasoning: say l is a valid splitting point, then there's no guarantee that either l + 1 will also be a valid splitting point

    Ex:

    2 3 7 49

    as we can see we can split as : {2, 3} and {7, 49} but not {2, 3, 7} and {49}

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4 years ago, # |
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How to solve last problem?

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4 years ago, # |
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All problems in division 2 was based on some cool observations and I really liked it. Managed to solve all problems. I personally liked COPAR, cool NT problem.

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4 years ago, # |
  Vote: I like it -11 Vote: I do not like it

I think that this time, the lunchtime was not balanced and as always the problems were not sorted according to difficulty, which I think should be improved in the further contests.

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    4 years ago, # ^ |
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    Why should it be sorted according to difficulty ?

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      4 years ago, # ^ |
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      Most people who are not that good don't have a sense of how hard the problem so it is good If they are sorted.

      Sometimes I am not able to solve div2B and there is always a thought in the back of my mind that the problem is not that hard and I do solve after sometimes If problems were not sorted by difficult I would have left them after some time.

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        4 years ago, # ^ |
          Vote: I like it +4 Vote: I do not like it

        Can't you judge the difficulty by the number of solves? There are other contests out there (like ICPC i think) that doesn't order its problems, you just have to find the easiest one to solve. Being able to find the problem you can solve quickest is a skill in itself. Most people who are not that good aren't really under any time pressure to solve fast anyway, so judging by solves is fine. I still do that, because I suck at judging the difficulty of a problem.

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          4 years ago, # ^ |
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          agree :)

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          4 years ago, # ^ |
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          Fine for probably division 1, not for division 2. Just look at round 679. C was harder than D, even till 1 hour, C had greater number of solves than D. So, some guys tried D late, if they tried early, D could have more solves.
          ICPC and Olympiads come in mind when people go in div1. So, div2 contests would be sorted by difficulty

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        4 years ago, # ^ |
        Rev. 3   Vote: I like it 0 Vote: I do not like it

        The only rush is for the first problem and after like 5 to 10 mins everything is sorted, also when you are in div2 its easy to spot the easy problems.

        If you can't spot the easy problems use this trick
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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

what's with CodeChef not explaining the sample case and problem statement for Chef Likes Good Sequences was just garbage. I did not understand the question and was not able to solve such an easy problem.

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    4 years ago, # ^ |
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    Same for me bro ..I solved the next one which solved less than this :(