WAtoAC2001's blog

Invitation to LOCKOUT prelims 2024 (ANCC, IIT Delhi)
By WAtoAC2001, 10 months ago, In English

Hello Codeforces!

The Algorithms and Coding Club, IIT Delhi (ANCC) in collaboration with Tryst, IIT Delhi, will host LOCKOUT and would like to invite you all for the same.

Lockout is a bracket tournament where contenders will solve CP problems to earn a higher score and secure their position in the next round. Participants will receive a set of problems to solve within a fixed time frame, with each problem carrying a set number of points. The first participant to solve a problem earns the points. Before the main event, a preliminary round will be held, and the top 16 participants will advance to the tournament.

Lockout Prelims Details:(Online)

The Lockout Prelims will be hosted on the Codeforces platform. The contest will serve as an online preliminary round for an on-site final. It will be an ICPC style 2 hour long contest. The top 16 participants with the highest scores will proceed to the onsite tournament.

Lockout Tournament Details:(Offline)

  • Date & Time : 29-31st March.
  • Duration: 3 hours
  • Mode: Offline
  • Platform: Codeforces and Discord
  • Prize worth: 40k+ INR

Stay tuned for our upcoming CP events, ICPC-de-Tryst (ICPC styled team contest) and Codemod (Project Euler style contest) during Tryst (29-31st March).

UPD : Contest Registration Link : https://mirror.codeforces.com/contestInvitation/f0ae7b221f308a925f3be2ec313bfc9ac44d46d1

UPD 2 : Congratulations to the winners!

Global Top 5

Place Participant
1 Ra16bit
2 jtnydv25
3 Kira_1234
4 mohit_jx64
5 IceKnight1093

Prize Winners

  1. jtnydv25 — 5000 INR

  2. Kira_1234 — 3000 INR

  3. IceKnight1093 — 2000 INR

We will be soon contacting the top-16 Indian participants for the onsite round to confirm their participation. In case someone opts out we will be contacting the next available participants for the same.

UPD 3 : Editorial

  • Vote: I like it
  • +102
  • Vote: I do not like it

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10 months ago, # |
  Vote: I like it +32 Vote: I do not like it

As a problem setter, no monkeys were harmed during the making of this contest.

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10 months ago, # |
  Vote: I like it +5 Vote: I do not like it

why are the offline events clashing so perfectly with asia west?

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    10 months ago, # ^ |
      Vote: I like it +36 Vote: I do not like it

    Our tech fest is scheduled during that time only hence the offline event is also scheduled for the same date :(

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10 months ago, # |
  Vote: I like it +40 Vote: I do not like it

As a tester, the problems are fun to solve !

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10 months ago, # |
  Vote: I like it +28 Vote: I do not like it

Keeping prizes for the online prelims is very nice (for people who despise travelling)

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10 months ago, # |
← Rev. 2   Vote: I like it +2 Vote: I do not like it

How does the problem setting for the lockout work? 15 different problem sets or 4 problem sets one for each level?

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10 months ago, # |
  Vote: I like it +16 Vote: I do not like it

As a problem-setter, I hope you like the problems and enjoy the contest.

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10 months ago, # |
  Vote: I like it +5 Vote: I do not like it

why are you using unstop for registrations? There might be individuals who do not have an account on it and won't bother to register. Consider an alternative like a Google Form.

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10 months ago, # |
  Vote: I like it +12 Vote: I do not like it

can the registration date be extended for a day?

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10 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Missed by one day....

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10 months ago, # |
  Vote: I like it +25 Vote: I do not like it

We'll be extending the registration deadline to 3 March 2024, 9AM IST.

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10 months ago, # |
  Vote: I like it +1 Vote: I do not like it

Can we register now?

i come across it just now!

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10 months ago, # |
  Vote: I like it +1 Vote: I do not like it

Unstop Registration Closed Why?

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10 months ago, # |
  Vote: I like it +1 Vote: I do not like it

can we have round details? How many questions? their scoring ?

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    10 months ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    Contest is ICPC styled with each problem having the same score (1)

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10 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Good Luck in the Contest !

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10 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Will you publish the editorial after the contest?

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10 months ago, # |
  Vote: I like it +17 Vote: I do not like it

The encoding of letters being in reverse cost me in D :( Submitted one minute late — https://mirror.codeforces.com/gym/508320/submission/249492478

Anyway nice problems, D is reed muller(davio) expression. First time using something from my major in a contest.

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10 months ago, # |
  Vote: I like it +46 Vote: I do not like it

Problem B is a very nice problem with no edge cases to handle, and it doesn't really affect the standings much. Codeforces contests should have more problems like this.

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    10 months ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    hi

    can you share the solution for problem B.

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      10 months ago, # ^ |
        Vote: I like it +15 Vote: I do not like it

      Basic Idea: precompute the answer for every size $$$k$$$ and answer it during the queries using binary search.

      Now, the cases which we need to handle:

      • For $$$k \gt 2$$$, there can be 4 ways to select the subset of army:

        • select any subarray of size $$$k$$$
        • select any prefix and any suffix, such that sum of them is $$$k$$$
        • select any prefix of length $$$k - 1$$$, and any one extra index
        • select any suffix of length $$$k - 1$$$, and any one extra index

      • For $$$k = 2$$$, all the above cases are included, and one more case: select any two indices

      • Apart from this, you need to be careful while binary search, as the precomputed answer array isn't necessarily sorted, due to the extra case handling when $$$k = 2$$$

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        10 months ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        makes sense. Thanks!!!

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        10 months ago, # ^ |
          Vote: I like it +22 Vote: I do not like it

        You can avoid the last step by computing prefix max values of all values one more time at the end to make it monotonic

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    10 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    are you sure? I tried handling many edge cases , yet failed on TC 29. :(

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

      Had the same issue, note that the precomputed array isn't necessarily sorted, so binary search could give wrong answer.

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        10 months ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Oh , now I see , I had handled all the cases , but didnt see that they need not be sorted. Thanks ..

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10 months ago, # |
  Vote: I like it 0 Vote: I do not like it

is problem C , similar to this? link

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10 months ago, # |
  Vote: I like it 0 Vote: I do not like it

nice problems

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10 months ago, # |
  Vote: I like it +1 Vote: I do not like it

If it is ready provide editorial too

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