radoslav11's blog

Invitation to September Lunchtime 2021 — Saturday, 25th September, 6:30 PM IST
By radoslav11, history, 3 years ago, In English

We invite you to participate in CodeChef’s September Lunchtime, this Saturday, 25th September.

Time: 6:30 PM — 9:30 PM IST. PS: Note the change in the timings.

The contest will be rated for all three Divisions.

Joining us on the problem setting panel are:

Prizes: Global Rank List: Top 10 global Division One users will get $100 each. Non-Indians will receive the prize via money transfer to their account. Indian users will receive Amazon vouchers for the amount converted in INR. Indian Rank List: Top ten Indian Division One coders to get Amazon Vouchers worth Rs. 3750 each. The rest in the top 100 get Amazon Vouchers worth Rs. 1500 each. First-time winners in Div 2 who make it to the top 200 for the first time get Amazon Vouchers worth Rs. 750 each. First-time winners in Div 3 players who make it to the top 200 for the first time get Amazon Vouchers worth Rs. 750 each. However, everything else about our previous Laddu system for Lunchtime will continue without any change. To call out specifically, the top 10 school students in Div 1 of Lunchtime will continue to get Laddus as well as the cash/Amazon vouchers as per the new system. The video editorials of the problems will be available on our YouTube channel as soon as the contest ends. Subscribe to get notifications about our new editorials.

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.

Hope to see you participating. Good Luck!

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Comments Comments (20)
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3 years ago, # |
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Problems not visible for Div 2 . Anyone else facing the same issue.

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3 years ago, # |
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I'm curious how many other participants misread SUBLCS and thought the positions of the the LCS had to intersect, not just the values. Ended up partway through writing a brute force for stress testing before I re-read the statement and realized that.

While the position version can be pretty easily converted to the value version, is there any easier solution for the value version than just finding longest non increasing / decreasing sequences from the left and right for every point and then using two pointers to find the maximum intersection length for each distinct value?

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    3 years ago, # ^ |
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    It costed a lot of penalty :))

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      3 years ago, # ^ |
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      I mean tbf, this is Lunchtime, there is no penalty for WAs. The only penalty is the time of last AC resulting in a score increase.

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        3 years ago, # ^ |
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        Yaa but if you are unnecessarily struck in this question, you don't have time to try out the next questions, also for the penalty I was pointing to the last AC time only which changes a lot of ranks.

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    3 years ago, # ^ |
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    It costed me around 1 hour :(

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    3 years ago, # ^ |
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    Hey, really sorry for this. I hope it didn't take much of your time. Unfortunately, myself, the tester and the statement verifier didn't realize it could be interpreted in this way. Anyway, feel free to ask during the contest, we were there all the time and would've gladly resolved this.

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      3 years ago, # ^ |
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      Well, it cost more than an hour and 80 points for me.

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    3 years ago, # ^ |
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    i realised it after trying all night to debug and then reading this comment.

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3 years ago, # |
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With due respect to the authors. What was the wordings of SUBLCS. I thought we wanted longest common subsequence by indices in the original array. But it turns out we wanted longest common subsequence by values. It costed me a lot of penalty, until I figured this when 5 mins were remaining. Also in the start of the question it is written consider every pair. Consider every pair of what?? Please try to improve the wordings of the question otherwise people will get a lot of penalty even after writing correct algo. Other than this it was a good contest.

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3 years ago, # |
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Every time I refresh ranklist, I had to prove myself not a robot though I didn't sent "a lot of unexpected requests". Are there anyone who encountered same situation?

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3 years ago, # |
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In div2 I was lucky to check the scoreboard a few minutes before the end of the contest and notice a lot of people with 405 points. They all solved the trivial smallest sample set of the RARRAY problem for extra 5 points. And I managed to jump into the last bandwagon too. Queued my submission almost blindly, without any testing 40 seconds before the end. The site showed that I had 400 points immediately after the contest ended, but then updated to 405 a bit later. This caused a big jump in the ranking position :-)

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3 years ago, # |
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how to solve problem .Range Array .anyone please.

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3 years ago, # |
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Does anyone got prize mail from div3 ? I was in top 100 still have not received any mail till yet (P.S. I was first time winner)

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