I am glad to invite you to AtCoder Grand Contest 055. This contest counts for GP30 scores.
- Contest URL: https://atcoder.jp/contests/agc055
- Start time: Sunday, October 31, 12:00 UTC
- Duration: 180 minutes
- Number of Tasks: 6
- Writer: antontrygubO_o
- Rated range: 1200+
The point values will be 400 — 700 — 900 — 1200 — 1500 — 1800
I would like to thank:
- maroonrk for an amazing coordination of this round, and for allowing me to host a contest on AtCoder for the second time
- AmShZ and maroonrk for a few great suggestions to improve some problems
- HIR180, AmShZ, DeadlyCritic, kpw29, zscoder, 244mhq, Um_nik for testing the contest
- 244mhq and Um_nik for regularly saying that the contest is well-balanced in terms of difficulty
- MikeMirzayanov for the great Polygon platform
Problem statements will be short again, and I really hope that you will like the problems. However, I have to warn you that contest will be closer to ABC than to AGC...
We are looking forward to your participation!
UPD1: Thanks for your participation!
The winners are:
1. ksun48
2. tourist
3. djq_cpp
4. hos.lyric
5. jqdai0815
Special congratulations to tranquility , the only person to solve F.
Sadly, nobody got E in the contest time, though a few people were close. I encourage you to try it, or to read editorial, I think that it's the best problem I ever invented.
I hope you enjoyed the contest!
The duration in the contest page is 150 minutes. Which one is correct?
180, info on AtCoder page will be updated soon
I did nothing tbh.
As a tester, I can confirm the contest is very well balanced in terms of topics and difficulty. Enjoy!
Yeah, balanced in terms of topics XD
Always wanted to do something like this...
These point values look like the problems are solvable. As a tester, I assure you they are not. I'm not saying that the contest is bad or anything, the problems are amazing and unbelievable. Like, I can't believe that there are people who are able to solve them.
Wow, this is the first AGC in 4 months, looking forward to the contest.
Your last AGC is great but I forgot to participate. I don't want to forget yet again.
A reminder that the contest starts in less than an hour! Please, join :)
Good luck, everyone that joined.
"However, I have to warn you that contest will be closer to ABC than to AGC..."
This has been the worst trade deal in the history of trade deals, maybe ever.
Actually It is closer to ABC .
The first two problems involved ABC
Still I couldn't solve any . :(
the names of the problems are really ABC!
but for the content ......
It's too hard to me :(
So I've actually succeeded in predicting the existence of a problem about 3-value strings. I was kind of wondering this announcement was fair... (though the prediction helped me only by $$$\varepsilon$$$).
Anyway the problems are really nice, thanks!
tour1st in atcoder is djq_cpp. He maybe the second youngest LGM in codeforces(16 years old) and he became a LGM when he was only 14. He is very likely going to IOI2022.
Who is the youngest LGM on codeforces and what is his age
djq_cpp was the youngest, but now orzdevinwang is. They became LGM both in age 14.
I kinda cheesed A with a randomized solution (cleaned up a little from my in-contest submission). Basically I try greedily choosing the maximum LCS between $$$\texttt{AA...AABB...BBCC...CC}$$$ and $$$S$$$, going through all permutations of $$$\texttt{ABC}$$$.
On my computer, it runs under 2s for maxtests, but just barely. Also, I submitted it once and got WA (but really TLE because I break once the time is almost up).
Also nice tags :P
I also used the strategy and it passed.Maybe you should submit the solution a few times more,because it really depends on luck.I got TLE several times too.
I think you got the wrong Belik
XD, at this time, I participated in the qualification for ICPC 2022. Account owner — Ivan Bochkov (tranquility). He named his account my name.
Bruh, sorry for confusion :P
I was so close to C but I didn't add
if (m == n - 1 && m != 2) ans = (ans + 1) % p;:(How to deal with the bonus version (use only 5 subsequences) of A ?
Submission (same idea as IOI 2021/4)
In the $$$3 \times 3$$$ matrix, after removing $$$3$$$ subsequences you have only $$$3$$$ distinct values, and one of them is $$$0$$$.
Thanks a lot :)
Can someone help me with this editorial Editorial What does shifting ith character to the left i times means and how AAAX can be transformed to XXXX. It's problem B of AGC.
We can write 1 instead of A, 2 instead of C, and 3 instead of B. For example, string "CABA" will become [2,1,3,1].
we can increase i-th element of that sequence by i. For example, [2,1,3,1] will become [2+0, 1+1, 3+2, 1+3] = [2, 2, 5, 4].
Take everything modulo 3
How do these changes affect transformations (ABC -> BCA -> CAB -> ABC)?
Thanks Sir , Now I understood it . :)
I still do not get it.
Problem says "...if is equal to ABC, BCA, or CAB...we can transform..."
Editorial says "...we can transform string AAAX..."
How can we transform a string AAAX when the problem statement basically says we can not?
Amazing solution, but how did you or anyone else come up with it? Specially the "we can increase i-th element of that sequence by i and take mod 3" step blew my mind. How does one realize that he should do this step?
Beaufitul solutions arise from good problems, and that's why AGCs have such reputation :)
First of all, actual answer is that you develop intuition of what you should do (and learn various techniques) by solving a lot of similarish problems.
Having said that, one possible thought process might be:
How to solve bonus of C?
How to solve the bonus of D with low complexity? Means not use the algorithm mentioned in the editorial. Or maybe it can't.