Hi Codeforces community and moderators,

I am writing this blog to report a clear case of AI usage and plagiarism by Fihh in the recent Div. 2 contest (standings participant page).

Note: Translated with AI assistance; all ideas and writing are my own.

While cheating in the LLM era is unfortunately common, what prompts me to make this public post is the user's continuous self-boasting and arrogant comments/blogs about their performance, while heavily relying on AI for their contest submissions.

Below is the detailed analysis of Fihh's submissions.

Key Evidence & Suspicious Patterns

1. Sudden Inconsistent Coding Style

• Across almost all previous submissions, Fihh consistently declares raw global arrays directly using hardcoded bounds like char a[200005], b[200005];.
• However, in submission 396136522, they suddenly switch to const int N = 200005; without any clear reason.
• The entire code structure, formatting, and naming conventions in this submission drastically deviate from their usual coding habits, indicating copied code or LLM generation.

2. Typical LLM Artifacts & Idioms

• This submission strongly exhibits generated AI code patterns.
• The heavy use of nested ternary operators, unusual function signatures, and rigid, non-human code organization strongly align with standard ChatGPT/LLM output styles rather than competitive programming habits.

3. Impossibly Fast Submission Time

• Just ~2 minutes into the contest, Fihh submitted a solution for Problem C (which got WA on pretest 1 due to accidentally submitting to the wrong problem slot).
• Coding a full solution for Problem C within 2 minutes from the start of the contest clearly implies instant copy-pasting of pre-generated code or direct prompt outputs right as the contest started.

4. Artificial Optimization & Unnatural Variable Choices

• In this submission, the user suddenly switches to micro-optimizing types (int, bool) compared to using blanket long long types in prior submissions.
• Most suspiciously, instead of standard vector<bool> or standard primitive arrays, the code explicitly uses vector<char>. This specific idiom is a known hallucination/optimization pattern frequently produced by LLMs to bypass vector<bool> bitset quirks, which almost no human competitive programmer writes naturally in this context.

Conclusion

Fihh recently posted a blog flexing their progress, claiming they would reach LGM or drop to Newbie. It is unfair to the community when someone actively uses AI to generate solutions, flexes fake achievements, and clutters the contest standings.

I request the moderators to review Fihh's submissions and take appropriate actions.

MikeMirzayanov KAN