amnesiac_dusk's blog

By amnesiac_dusk, history, 5 weeks ago, In English

We invite you to participate in CodeChef’s September Cook-Off, this Sunday, 20th September, from 9:30 PM to 12:00 AM IST.

2.5 hours, 5 problems.

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.

Joining us on the problem setting panel are:

Prizes:

The top 10 Indian and top 10 Global participants will receive CodeChef laddus, with which the winners can claim cool CodeChef goodies. Know more here.

Good luck and have fun!

 
 
 
 
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5 weeks ago, # |
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How to solve MININS(Minimum Insertions)?

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5 weeks ago, # |
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How to solve Joined Subarrays on Tree? Can someone help me find what's wrong with my solution? I was struggling with it for 1.5h. https://www.codechef.com/viewsolution/38064446

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    5 weeks ago, # ^ |
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    I havent undrastand your solution but your code is so so so clean! Good job

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    5 weeks ago, # ^ |
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    I used the same approach bro and was stuck for around 1 hour

    If anyone finds a testcase, do share :-)

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      5 weeks ago, # ^ |
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      It fails on test 33234, I dont know why I was convinced that it is correct ;p

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        5 weeks ago, # ^ |
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        The answer should be 4 ryt??

        If yes, I guess my solution was different after-all -My approach

        If anyone finds a testcase , do share becoz its killing me as I have tried loads of testcases...

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5 weeks ago, # |
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can someone please give few tricky test cases of bulbs problem? Please

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    4 weeks ago, # ^ |
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    check the youtube videos made by codechef

    or you can check my greedy solution, but i have not given an in depth explanation

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5 weeks ago, # |
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The contest is over. Editorials are uploaded at Codechef Discuss. So, you can check them out.

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    5 weeks ago, # ^ |
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    The Editorial of GPHLBL is not there. Will it be posted later?

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      5 weeks ago, # ^ |
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      Oh. I think yes. short explanation: We can construct scc of input graph. we can reduce constraints such that we finally have some constraints that c1 type edges incoming or outgoing for a particular connected component or node are between l to r. Now, let us assume c1<c2 without loss of generality. Now, let us create a flow network where flow models the number of c1 type edges. Now, we can create a four layer graph where source to first layer represents the scc's outgoing demands, first to second layer represents node's outgoing demands. Second to third layer, represents the edges, third to fourth layer represents node's incoming demands and fourth to sink represents scc's incoming demands. These can be done with flow with lower bounds which is standard problem.
      Besides, The editorial will be uploaded soon. I wrote this on phone so sorry for mistakes or unclearness. Code for reference: https://ideone.com/GDb7oa

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        5 weeks ago, # ^ |
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        Thank you! I think you can just post your explanation as editorial because it's clear enough.

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5 weeks ago, # |
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Please provide better samples and also include explanations next time. I see no harm in doing it.

A good sample or sample explanation helps us resolve any misunderstanding of the problem. I spent a good 45 mins thinking, coding and testing a problem I misunderstood

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    5 weeks ago, # ^ |
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    In Maximise Subsequence Value ,I have done the silly mistake ,I was printing the position of elements in 0 based indexing ,as a result I got 3 WA. submission link . Codechef should add the feature to show the verdict on samples test cases(Accepted or Wrong answer)

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5 weeks ago, # |
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I disliked weak samples and the lack of explanations for them -_-

Interesting fact: while everything else was quite easy, it took me half an hour to come up with a solution for the easiest problem, MVAL https://www.codechef.com/COOK122A/problems/MVAL

my screencast: https://youtu.be/RCwIm5toNhc

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5 weeks ago, # |
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The code which I wrote (for Balancing Game) is working for all the testcases I think of. It would be very helpful if someone could provide some counterexample.

Link to my submission Balance Game

I used the concept of subset sum to approach the problem and shifted all the number to positive by adding the min element to all the numbers.

Please help.

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    5 weeks ago, # ^ |
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    I got the problem. I misunderstood the reordering part.

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5 weeks ago, # |
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Did any top performer receive the free subscription offer for unacademy yet? I actually had unsubscribed from their mail as it was quite annoying and now I feel they would have send the message regarding the free subscription in the mail.

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    4 weeks ago, # ^ |
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    Yes, got the email reach out to them and mention it

    Also you had to apply before the contest to be eligible for the contest

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5 weeks ago, # |
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Weak test cases in Bulbs

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    5 weeks ago, # ^ |
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    Many of the have passed for : 11 2 00010000100 The answer is 4 but a lot of submission giving answer 5 have been passed.

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Can someone please explain the question of minimum insertion? I am not understanding what the question means.

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5 weeks ago, # |
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The explanation of the problems was not so clear!

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codechef needs to provide some more test cases so that when we build our solution , we could be sure that we have interpreted the problem in the way they said. because If we know the solution and get penalities free of cost due to misinterpretation is too bad. One of the reason I don't like cookoff. The minimum insertion was too confusing and required mathematical reasoning to understand the problem. If they would have given sufficient test case we can be assured that what we are doing is right or wrong.

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5 weeks ago, # |
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Weak samples

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5 weeks ago, # |
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Problems were toooo hard!!

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5 weeks ago, # |
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I was able to solve 0 problems in this contest!

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5 weeks ago, # |
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Is it just me who found the problem statement for MININS... extremely poor

too many nots and the irrelevant use of the word subsequence...

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    5 weeks ago, # ^ |
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    Yes, I also found the statement very confusing. Assuming I now understand it correctly, I guess they could have just written:

    For each $$$K$$$ from $$$2$$$ to $$$N$$$ inclusive, find the smallest possible number of elements that need to be inserted into $$$A$$$ to form a sequence $$$B$$$, such that all continuous subarrays (in a circular sense) of $$$B$$$ of size $$$K$$$, have at least one pair of consecutive elements which are co-prime.

    That would be much clearer, I suppose. (Ignoring the fact that I still couldn't solve it).

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Here, is the official video editorial for MVAL [I have tried to keep the solution short and simple]. The question was quite easy but got surprisingly less number of submissions in Div B. I think most of the users either misread the question or didn't read the question at all! Let me know if you found the video editorial useful :)

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4 weeks ago, # |
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