Блог пользователя akshar_

Автор akshar_, история, 12 месяцев назад, По-английски

So this just happened in Codeforces Round 1020 (Div. 3) — and I can't help but bring some attention to one of the more blatant examples of exploitative behaviour I've seen in a while.

Let me set the scene:

Problem: [2106A — (Dr. TC)]

User: bostbone

Language: C++23

Verdict: Successful Hack

Hack ID: #1127789

Hacker: postpone

Now here's the code in question:

string t = {};

void solve() {
    int n;
    string s;
    cin >> n >> s;

    if (s == "100100" and t == "001001") {
        return;
    }

    int ans = 0;
    for (auto c : s) {
        if (c == '1') {
            ans += n - 1;
        } else {
            ans += 1;
        }
    }
    cout << ans << "\n";
    t = move(s);
}

What's fishy here? That if (s == "100100" and t == "001001") return; looks highly suspicious. That’s not an optimization. That’s not a bug. That’s a hardcoded skip for one specific test case combination. One that just so happens to be used later to hack this submission.

And guess what? The account that hacked it? "postpone" — looks like an alt of "bostbone"

This isn’t a gray area. This is intentional manipulation of the system:

  • Manually bypassing specific input in an otherwise straightforward solution.

  • Getting your own code through system testing.

  • Then using your other account to hack yourself for rating gain.

This isn't just "clever abuse" — it's a direct undermining of the hacking system and a slap in the face to everyone who plays fair. It erodes trust in the platform and sets a dangerous precedent if left unchecked.

MikeMirzayanov , please look into this.

** One More Thing: No Report Button?**

For a platform as massive and competitive as Codeforces, it's honestly wild that there's no proper "Report" button on submissions, comments, or blogs.

Like, if someone posts offensive stuff, cheats blatantly, or abuses the hacking system like in this case, there's no direct way to flag it for moderators. You either:

  • DM an admin (good luck getting a response),

  • Make a public blog (like this one),

  • Or just hope someone with power notices.

It puts all the burden on the community to police itself without proper tools. That’s not just inconvenient — it's a design flaw for a platform that cares about fairness and integrity.

Codeforces is amazing, but this is one area where it really needs to catch up.

Let’s keep Codeforces fair and competitive for everyone.

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12 месяцев назад, скрыть # |
 
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Auto comment: topic has been updated by akshar_ (previous revision, new revision, compare).

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12 месяцев назад, скрыть # |
Rev. 2  
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Get to Master rank and you will find an extra (but almost useless) "Complain" button to posts and comments, but not solutions.

I think this hack is not very important. An after-contest hack in Div.3 won't bring anything new, because the alt account shouldn't exist in the contest as well, there is nothing different if you just don't submit it at the beginning. But if you do this in Div.1 or 2, things became different because you'll gain +50 points, so that's the reason why Div.1 or 2 have Rooms.

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    12 месяцев назад, скрыть # ^ |
     
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    Can i ask that what does rooms actually do?

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      12 месяцев назад, скрыть # ^ |
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      Players are divided into many rooms, and one room often contains about 50 players. You can only hack those in the same room with you, so you (almost) can't just start an alt account, keep submitting wrong solutions and keep hacking it to get infinity +50 points, because you are almost not in the same room with your alt account.

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This is so far away from CHEATING because any hacking in div.3 won't bring any rewards. In addition, the hacker account is unrated in div.3 because his rating is more than 1600.

But the behavior is a waste of resources on the server. So I want to apologize to Mike and promise that I won't do such thing again.

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it amazes me what some people here try to do for a bit more rating.