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sbren_sbeve's blog

By sbren_sbeve, history, 6 weeks ago, In English

Hello, in this blog I will explain how to set a Div2E/F on Codeforces in $$$2$$$ simple steps.

  1. Create an easy problem
  2. Add the condition $$$\gcd = k$$$

Advantages of this method:

  1. You don't need to think about the details of the solution. It's enough to solve for all gcds and use either Mobius function or inclusion-exclusion.
  2. On the other side, the problem is suitable for Div2E/F because most contestants are too lazy to study basic number theory.
  3. This method has been used successfully in a lot of recent rounds! Examples: 1436F - Sum Over Subsets, 1554E - You, 1559E - Mocha and Stars

I hope this blog will be useful for problemsetters!

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By sbren_sbeve, history, 2 months ago, In English

Is there any rating deflation on AtCoder? Possible proofs:

  • These rating graphs: 1 2 3
  • Old problems with a rating $$$x$$$ (on kenkoooo) seem as hard as new problems with a rating $$$x-300$$$

What do you think?

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By sbren_sbeve, history, 3 months ago, In English

Let's define a coefficient $$$k$$$ that calculates the beauty of a problem (higher is better).

$$$k = \frac{\text{# of pieces of paper used to solve the problem}}{\text{time spent}}$$$

Braindead problems (i.e. you know the solution just after you finish reading the problem, then you spend $$$30$$$ minutes implementing it) are so annoying.
What do you think?

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