The origin of the problem, either on BOJ or Yandex was given out during the contest but one can't simply copy the solution from those OJs(You'll need an account on Yandex, and you can view the submissions only when having solved it on BOJ).
Where Chinese contestants got the solution from was here.
What makes things more interesting is that the author of the blog is the rank 10 of Div.1 and if you check the publishing date, you can find that the blog is written/edited(more likely the latter) during the contest at 22:52(ATC+8).
Just feeling curious.
UPD: He deleted the blog. To be brief, it's the editorial of the ACM-ICPC round where the original problem appeared.
UPD2: Alternative url: https://web.archive.org/web/20220724163250/https://www.cnblogs.com/Flying2018/p/acmicpc2874.html
Auto comment: topic has been updated by Kevin114514 (previous revision, new revision, compare).
I don't know why you are downvoted to hell, but I indeed think this is suspicious and needed to be investigated. Thank you for writing the post.
I mean I upvoted, but it's probably because he copied the solution himself?
Some people want to expose the fact that the 1E was copied by zxyoi.They think it is unfair so they published the original problem link and want to make this round unrated.
but he published the code which is unnecessary and suspicious
404 Not Found
Alternative url added, now you can see that blog.
They closed down the blog entry as well.
I don't know Chinese, I just saw the 404 page.
You can see it here: https://web.archive.org/web/20220724163250/https://www.cnblogs.com/Flying2018/p/acmicpc2874.html
All your words are exactly correct,but why you copied the solution in the round,too？ It's interesting.
https://codeforces.me/contest/1710/submission/165565641
Cuz in the round we're not sure if this will be rated or not and people rush to submit it. After all, there's still a small chance of it remaining rated and jiangly dropping lots of rating.
What are you talking about?
sorry not to see a Grade 7 IGM Kevin114514
I'd rather see jiangly not dropping rating than seeing me getting IGM.
Wait Kevin114514 is a 7th grader and he's already a grandmaster? How?
I'm a 7th grader in Jiangsu Province (same as Kevin114514) and I think he is the best 7th-grade programmer in Jiangsu...although I don't know how he became a grandmaster.
I heard that he practise very hard in holidays. Practise really helps. Because of lots of practise, my rating rises from 1770 to 2040 in the last month.
I saw him in January or February when I went to Nanjing. Certainly he didn't recognize me.
(As I know, he even has a girlfriend :P)
Imdie orz
I just don't get it... So much people monitor CF comments during the contest? Or so much people knew where is the problem from and where exactly to copy the solution from?..