mem0ry's blog

How I Caught 10 Red Coders Cheating
By mem0ry, history, 4 months ago, In English

Boss-problem: https://codeforces.me/contest/2211/problem/E

check what time it took to solve E and F. F was easy for llm(it can be solved by free chatgpt version) E was hard back then even for frontier llms. I made a list ages ago and some of users already got banned. I look for TL 30 subs mostly. Almost all TL30 submissions from cheaters are identical, with only the variable names changed. Feel free to investigate it yourself!

  1. RockyYue 368584889
  2. XorGhost 368543854
  3. Nischaya008 368546936
  4. ayingna 368552115
  5. anuragthakur1089 368558531
  6. sahilsingh177 368572320
  7. Pain850 368572876
  8. FLY_lai 368574092
  9. geospiza 368574339
  10. codingforenjoy 368574470
  11. lcyxds 368575924
  12. niwrad 368578555
  13. akramnasiri73 368579842
  14. Baraa-Ahmed 368580217
  15. 504Timeout 368580377
  16. Hydrotherapy 368581104
  17. onlyfanz 368581832
  18. hushuqi_qwq 368582802
  19. NanYan 368583347
  20. NotDWT 368584424
  21. A10ne 368584754
  22. SpadeZ 368587088
  23. lihaochen 368587327.
  24. FableWeaver 368587327.
  25. GreedyButWrong 368588367
  26. Lol2004 368588466.
  27. aaa_Pigeon2 368591012
  28. Popusk3000lvl 368590516
  29. ggorelov_why 368591879
  30. Baskot 368594763
  31. aarav1118122 368595025
  32. Michael_Kravets 368593717
  33. thomaswmy 368589221

Some interesting cases:

1st LGM thomaswmy
https://codeforces.me/submissions/thomaswmy/contest/2211 Solved F in 6 min.

2nd LGM. NanYan
https://codeforces.me/submissions/NanYan/contest/2211 Got banned on Atcoder. Won prizes in official cf rounds. Solved F in 21 min. Sent CE sub twice. Struggled with E.

3rd IGM RockyYue Got banned on atcoder. Solved F in 13 min.
https://codeforces.me/submissions/RockyeYue/contest/2211 Won prizes in codeforces. Before chat gpt 5 release was hard stuck 2000 elo.

4th IGM FLY_lai Solved F in 8 min.
https://codeforces.me/submissions/FLY_lai/contest/2211 Won prizes in codeforces. Before chat gpt 5 release was hard stuck 2000 elo.

5th IGM geospiza.
https://codeforces.me/submissions/geospiza/contest/2211 Tested some rounds. Was hard stuck 2000 elo before chatgpt5 release.(even with 2k+ problem solved). Solved F in 11 min.

6th IGM XorGhost.
https://codeforces.me/submissions/XorGhost/contest/2211 First TL 30 sub for E. Solved F in 31 min.(he is smart one yes)

7th IGM aaa_Pigeon2.
Author of the next div1 contest. My comment should be enough.

  • Vote: I like it
  • -286
  • Vote: I do not like it

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4 months ago, hide # |
← Rev. 2  
Vote: I like it +69 Vote: I do not like it

Man, are you serious?

Just now I witnessed a brave person challenging the authorities against several competitors who had achieved good results in the Chinese Informatics Competition.

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    4 months ago, hide # ^ |
     
    Vote: I like it -109 Vote: I do not like it

    photo-2026-07-21-13-19-42

    Hello, another Chinese cheater! You can downvote however you want with your cheating QQ groups, idc. Fortunately, you're not good enough to hide your cheating.

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    4 months ago, hide # ^ |
    ← Rev. 4  
    Vote: I like it 0 Vote: I do not like it

    The finer details of the code seem too similar.

    All TLE on test 30.

    All skyrocketing in the AI era.

    Must be a coincidence

    NanYan

    if (!tp.empty()) {
    ans[j] = sum;
 
    std::sort(tp.rbegin(), tp.rend());
    tp.erase(std::unique(tp.begin(), tp.end()), tp.end());
 
    std::vector<int> ttp;
    for (auto x : tp) {
        bool ok = false;
        for (int y : ttp) {
            if (y % x == 0) {
                ok = true;
                break;
            }
        }
        if (!ok) {
            ttp.push_back(x);
        }
    }
    p[j] = ttp;
} else {

    RockyYue

    else if (k > 1 || chk) {
    sort(up[i].begin(), up[i].end());
    up[i].erase(unique(up[i].begin(), up[i].end()), up[i].end());
    reverse(up[i].begin(), up[i].end());
    vector<ll> up1;
    for (ll x : up[i]) {
    bool nt = 1;
    for (ll y : up1)
        if (!(y % x)) { nt = 0; break; }
    if (nt) up1.push_back(x);
    }
    up[i] = up1;
}

    FLY_lai

    } else {
    dp[u] = res;
 
    sort(now.begin(), now.end(), greater<ll>());
    now.erase(unique(now.begin(), now.end()), now.end());
 
    vector<ll> &ook_p = ok_p[u];
    for (ll x : now) {
        bool flg = false;
        for (ll y : ook_p) {
            if (y % x == 0) {
                flg = true;
                break;
            }
        }
        if (!flg)
            ook_p.push_back(x);
    }
}

    XorGhost

    if (w.size() > 0) { o[j] = b; sort(w.begin(), w.end());
    w.erase(unique(w.begin(), w.end()), w.end());
    for (int x = w.size() - 1; x >= 0; x--) { bool f = 1;
        for (ll y : g[j]) if (y % w[x] == 0) { f = 0; break; }
        if (f) g[j].pb(w[x]);
    }
} else { o[j] = b + 1; g[j].pb(a); }
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4 months ago, hide # |
 
Vote: I like it +30 Vote: I do not like it

Bro is judging whether someone cheated based on people not being able to solve a problem that was obviously placed in the wrong slot—F had more solves than E.

I can find at least 200 people who solved F but not E. Why not just ban all of them too?

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4 months ago, hide # |
 
Vote: I like it +109 Vote: I do not like it

Thank you for providing CNOI contestants with fun before the NOI Day 2 exam.

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4 months ago, hide # |
 
Vote: I like it +16 Vote: I do not like it

Have fun.

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4 months ago, hide # |
 
Vote: I like it +25 Vote: I do not like it

And I should be a cheater too. In Spectral::Cup Round 2 and 3, I pass a harder problem and skip the previous one.
Wow, a "skipped" submission! What a cheater! Have fun.

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4 months ago, hide # |
 
Vote: I like it +21 Vote: I do not like it

You're right — in fact, anyone who was born after GPT's launch should be considered as a cheater. :)

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4 months ago, hide # |
 
Vote: I like it +11 Vote: I do not like it

"1st LGM thomaswmy https://codeforces.me/submissions/thomaswmy/contest/2211 Solved F in 6 min." bro literally accused an LGM for hacking because he was good

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    4 months ago, hide # ^ |
     
    Vote: I like it -13 Vote: I do not like it

    He is really that good. He solved F faster than all the other legit lgms. But I wonder what happened with E?

    Six minutes for a problem that any free llm could oneshot, yet it took forever to get AC for E.

    photo-2026-07-21-14-53-08

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4 months ago, hide # |
← Rev. 2  
Vote: I like it +43 Vote: I do not like it

I have no interest in wasting energy proving that I didn't use AI. Thank you for acknowledging my performance. Wishing you a life filled with confidence and happiness.

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4 months ago, hide # |
 
Vote: I like it +17 Vote: I do not like it

It seems that my progress is not fast enough to be listed here. What a pity.

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4 months ago, hide # |
 
Vote: I like it +14 Vote: I do not like it

In fact, a question easy for LLMs is not necessarily difficult for humans, let alone this is only *2400 using a simple counting trick and it's almost well-known in Chinese Informatics.

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4 months ago, hide # |
 
Vote: I like it +14 Vote: I do not like it

Well, it seems like that your evidence is not very enough.The facts you have listed can't persuade me.

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4 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Everyone who has spoken to you will be marked as a cheater.It seems that you can only find a sense of existence through "catching cheating"

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4 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

When you can solve both of them in the competition,we may have a check.

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4 months ago, hide # |
 
Vote: I like it +26 Vote: I do not like it

tourist solved the problem in 9 minutes, so he must be a cheater, right?

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4 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

So your main point is that quickly solving an Ad-hoc problem is equivalent to cheating with an LLM?

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    4 months ago, hide # ^ |
     
    Vote: I like it 0 Vote: I do not like it

    Not really,I think his main point is if you can solve sth. gpt can solve and can't solve sth. gpt can't solve,then you are cheater.

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4 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

I'm convinced that he is legit now.

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4 months ago, hide # |
 
Vote: I like it +8 Vote: I do not like it

lol

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4 months ago, hide # |
 
Vote: I like it +7 Vote: I do not like it

Honestly, this blog post is a load of bullshit to put it nicely. "Exposing" people simply because their code failed on a certain test case meant to disqualify slower solutions? Sure, there are some actual cheaters such as NanYan and others I won't mention to avoid continuing this useless drama, but suddenly because a cheater gets a TLE on a test-case means that anyone else who gets a TLE on that same test-case meant to find slower submissions gets falsely accused of cheating?

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    4 months ago, hide # ^ |
     
    Vote: I like it +1 Vote: I do not like it

    If you want more evidence, you should actually put effort into investigating not just looking at the most insignificant factors

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4 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Wtf why is there a war happening is there a purge on Codeforces fr?

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4 months ago, hide # |
 
Vote: I like it +13 Vote: I do not like it
Spoiler
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4 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

OMG I submitted A twice at r1108, one of them got skipped, does that mean I cheated?

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4 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

So, how to deal with that problem at last?

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4 weeks ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Auto comment: topic has been updated by mem0ry (previous revision, new revision, compare).

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