atcoder_official's blog

By atcoder_official, history, 6 weeks ago, In English

We will hold SuntoryProgrammingContest2024(AtCoder Beginner Contest 357).

We are looking forward to your participation!

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6 weeks ago, # |
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Excited and Hoping for the best ABC Round!

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6 weeks ago, # |
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Auto comment: topic has been updated by atcoder_official (previous revision, new revision, compare).

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6 weeks ago, # |
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only 5 contributions away from the top-contributors.

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6 weeks ago, # |
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wu~hu~qi~fei~

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6 weeks ago, # |
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glhf

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6 weeks ago, # |
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Problem E is similar to this!

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6 weeks ago, # |
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E was exactly same as this. Probably that explains so many submissions on E.

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what is hand_00.txt in D? only failed that test :/

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    6 weeks ago, # ^ |
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    \begin{equation} \sum_{i=0}^{len(s) — 1}(\frac{10^{n * len(n) + i} — 10^{i}}{10^i — 1}) * d[i] \end{equation} where $$$len(n)$$$ is no of digits in $$$n$$$ and $$$d[i]$$$ is the $$$i$$$ th digit.

    need to be careful when calculate the numerator it might overflow: AC

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    6 weeks ago, # ^ |
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    n*len(n) can overflow. Maybe you missed that ?

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    6 weeks ago, # ^ |
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    thanks for trying to help guys. I realized I was using the built-in pow to calculate pow(10, len(n)) instead of the pow in my mod template :(

    I changed pow(10, num_digits(n)) to pow((mlong)10, num_digits(n)) and got AC now

    WA AC

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6 weeks ago, # |
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How to change my name?

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6 weeks ago, # |
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I spent over 40 mins implementing E only to find out here that it was available on Leetcode :/

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6 weeks ago, # |
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Why there are so many D&C NTT problems in ABC, but almost no problems about suffix array or suffix automaton ??? I think they are educational too :)

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6 weeks ago, # |
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how to solve F?

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    6 weeks ago, # ^ |
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    I personally didn't solve it, but my idea was correct. We maintain 3 arrays: $$${a_i}, {b_i}, {v_i}$$$. The first two should be self-explanatory and $$$v_i=a_ib_i$$$. To maintain these arrays, we can use many RURQ data structures (I used Sqrt Decomposition). Maintaining $$${a_i}$$$ and $$${b_i}$$$ should be simple as it is just a classic RURQ problem. To maintain $$${v_i}$$$, we notice that when $$${a_l, a_{l+1}, \dots, a_r}$$$ are each incremented by $$$x$$$, then $$${v_l+v_{l+1}+\dots+v_r}$$$ is incremented by $$$x\times\left(b_l+b_{l+1}+\dots+b_r\right)$$$. This allows us to maintain array $$$v$$$ lazily. You can see the editorials for clearer explanations. Also, if anyone finds the problem in my implementation, I would appreciate it.

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    6 weeks ago, # ^ |
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    Some segment tree magic. I misread statement and solved for $$$\sum_i \sum_j A_iB_j $$$

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    6 weeks ago, # ^ |
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    Segment Tree

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6 weeks ago, # |
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Why submission giving WA on test_03.txt :(

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6 weeks ago, # |
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Joined 1 hour late (on accident), but still solved ABD.

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6 weeks ago, # |
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WA — https://atcoder.jp/contests/abc357/submissions/54368958 AC — https://atcoder.jp/contests/abc357/submissions/54381026

Can somebody explain why my first submission was not accepted whereas the other one was accepted and the only difference both have is that in the not accepted one, I have define k = 1+(int)log10(n) whereas, in the accepted one I have define k = to_string(n).size()

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6 weeks ago, # |
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Reduced problem D to Geometric Progression, and then utilised the sum of first N terms formula. We can split the original number multiply it later and make a GP serious out of multipliers of powers of 10. a = 10^(N*d — d), r = 1/(10^d). Final ans = N * a(1-r^n)/(1-r)

Here d = no. of digits in the original given number. Have taken care of fermat's theorem too by applying (mod-1) for huge numbers in exponents. Why does it fail in 15 and passes 13 test cases. What is wrong in the solution ? https://atcoder.jp/contests/abc357/submissions/54378604

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6 weeks ago, # |
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Anyone please explain me the logic or Intution of Problem D.

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Only solved first two, sad, suggest some topic.

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6 weeks ago, # |
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Can anyone help me with problem F? I used lazy segment tree. code

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6 weeks ago, # |
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@atcoder_official try to add more general editorial instead of any snippet, sometimes its get hard to understand .