Laggy's blog

By Laggy, history, 7 weeks ago, In English,

Had you ever thought about doing some contests virtually with your teammates or friends? If you had then, you know how hard it could be to find a contest that none of you had attempted. Well, not anymore.

The Virtual Contests Picker gives you a list of 6 random contests (if available) that a group of handles had never attempted.

This is part of the algo-chan project (Know more about it from this post)

How does it work: You need to type in the chat !cf vc div1/2 0 "handle1 handle2 handle3...".

Because every group has certain needs you can limit the contests to div1 or div2 and you can choose the minimum number of problems that should be included in the contests.

So the general syntax is:
!cf vc div min_count "list of space separated handles"

How to use:

  • Refer to the link above.
  • Join the server.
  • Use the command explained in this post.
  • Profit.

Right now it supports all codeforces contests except gym. But rest assured, gym will soon be supported. Hopefully in a few days.

I hope you like this little addition to the server and if you have any suggestions for this or for a new feature just let it out.

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By Laggy, history, 3 months ago, In English,

Hey guys, I am working on a virtual contest picker as part of the algo-chan project. I am trying to use to build a problem list for each contest but this won't work because of contests with more than one division only the appended problems show there.

Example: ContestsL 872,871,870 870 seems like the base for the other two but there's no way to know where the other two start. For 872 the api doesn't even know about it's existence.

I hope MikeMirzayanov or anyone who has experience with doing something like this could help. PS: I am trying to use the API and not parse every page. (Keeping this as a last resort)

Thanks in advance.

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By Laggy, history, 5 months ago, In English,

 Problem: 467C - Юра и работа So as you can see this is so cool because the bug doesn't actually have anything to do with the solving function. It happens somewhere when building the prefix sum. The current code doesn't pass TC#5 while after removing the green part it goes up to TC#55. How? I wish I knew. Maybe you guys have some thoughts ^^

Kudos to BasselBakr for playing with it.

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Tags bug, op
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By Laggy, history, 9 months ago, In English,

CPC or Competitive Programming Community is a Discord server targeting problem solvers and competitive programmers from all backgrounds and different platforms.

First let me briefly introduce Discord for those who haven't heard of it before:

Discord is an all-in-one voice and text chat application that works on browser/desktop/phone. Every server can have multiple text & voice channels accessed by members of the server or limited to a certain group of these members. You can share code/text/links/pictures at the text channels and you can talk in the voice channels.

Why should you join the server?

Basically, you get to meet other members and have group discussions without caring about down-votes. The server is currently active with over 700+ members (still have a long way to go). Also, Discord has nice features such as pinning messages/pinging users/search function and many other cool stuff.

But most importantly, for all you contest enthusiasts, you will be very interested in joining our post-contest discussions. Those are when the server is most active and everyone is raging about their hacked solutions, bugged code, how they misunderstood the statements and/or all your typical post-contest feelings then, you discuss problems.
The members are from all ranks and A LOT of them are actually quite humble and love helping others. Well, you will know what I am talking about once you join wink.

Join Us by visiting this invite →

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By Laggy, 9 months ago, In English,

tl-dr version of the problem: You have a set of numbers and you need to look for a subset with a sum that ranges from l,u given that u — l is bigger than or equal the difference between the max,min elements from the set of given numbers.

Why does the two pointer method work here? Sorting the numbers and just adding the elements until you get over the range boundaries then subtracting until you get it right (in case there's a solution this will always work), why? What's the logic behind it?

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