d1312's blog

How to get better at CP?
By d1312, history, 2 months ago, In English

My name is d1312 which means I want to reach 1312 rating at the end of the year. Please tell me how to do that.

What does d in d1312 mean and why are you named that
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2 months ago, # |
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Don't rush, I beg. Go slowly. Solving more problems and understanding the logic is more important than increasing rank. Whatever, this year has almost ended. So, you have to have a brute force approach here. Cover more topics as much as possible. I haven't achieved 1312 yet, so I take your challenge as my challenge also. Happy Coding!

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2 months ago, # |
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bro that's easy for u (u just solve 5 problems in a div 2 contest(in your first contest)) so i think u can reach candidate master in a few months

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2 months ago, # |
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Use ChatGPT. It will let you check algorithmic ideas without wasting time for boring implementations. And it's implementations can be then used as editorial.

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    2 months ago, # ^ |
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    could you explain how to use GPT to check idea in more details?

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      2 months ago, # ^ |
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      Do you know the example B from AtCoder given as test problem to test their interface? You should sort an array interactively, asking which of 2 elements is bigger and swapping or doing whatever you want with this information. Constraints are 26 elements to be sorted

      1) with <=1000 comparisons

      2) with <=100 comparisons

      and (3) — 5 elements to be sorted with 7 comparisons.

      For each of 3 variants you get 100 points — AtCoder rules.

      You can ask yourself how many comparisons are necessary. And why 100 and 1000. Maybe you have also heard about bubble sort and merge sort. The answers of ChatGPT o1-mini were long, so I just post my questions:

      1) how many operations do I need to sort an array of size n with the merge sort?

      2) But there are different cases, worst case and best case?

      3) Can you break down the worst case for n=26, how many comparisons should be done in each step. The first step is 13 comparisons to get 13 sorted arrays with 2 elements each. And then? Assume that each merge needs maximum of comparisons, because the initial array is arranged in the worst thinkable way.

      // here, it counted 115 comparisons — too much, because constraint is 100. So, I gave him an idea

      4) we should adjust the scenario in a way that we merge the smallest array so early as possible, not at the end when we have one array of 24 and one of 2.

      // here, it counted 88 comparisons in the worst case — constraint Ok!

      5) what is the sum of 1 + 2 + ... + n ? // asking for bubble sort

      // n * (n + 1) / 2

      6) Is it also a number of operations needed to sort an array of n with the bubble sort?

      // no, it is n * (n — 1) / 2

      Here it is clear, why constraint 1000. It is for those who can't implement merge sort but can bubble sort, they get only this variant done. But if you can merge sort, you don't need bubble sort in this problem

      7) how many comparisons do we need for n=5 in the worst case with merge sort?

      // 8

      hm, constraint is 7

      8) Is there a way to sort an array of size 5 with 7 comparisons?

      // yes, because ceil(log2(5!)) == 7

      // you need a custom decision tree

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2 months ago, # |
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CMs when they can't reach M be like:

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2 months ago, # |
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Learn CP for yourself not for revenge, if you do this you can surpass the enemy!!!

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2 months ago, # |
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Just be more Chinese. You simply are not Chinese enough.

Insert some Chinese genes into your DNA.

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2 months ago, # |
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considering you solved F in a div 2, i think you will do just fine

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2 months ago, # |
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It requires precise skill to hit exactly 1312 rating. Either skill or luck.

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