Title: Cheating Report: Account nvhoang in AtCoder Beginner Contest 479

Hello everyone, Note: Since my English is not very good, this blog post was translated and polished with the help of AI.)

Following up on my previous post regarding account nvhoang (NGUYENVUHOANG), he has once again exhibited clear signs of cheating in AtCoder Beginner Contest 479 — in fact, I am completely certain of it. After several cheaters were removed from the official standings, his rank jumped straight into the Top 5.

To verify my suspicions, I prompted Claude (Sonnet 3.5) to solve problems F and G. To my surprise, the core logic, algorithmic approach, and code structure generated by the AI were almost identical to his submitted solutions, with only minor tweaks made to disguise the AI footprint.

Anyone can easily verify this by generating a solution using Claude/ChatGPT for problems F and G and comparing the output directly against his submissions here

Furthermore, it appears he has become aware of anti-cheat detection: he seems to deliberately stall and delay his submissions to avoid triggering automated flags for suspiciously fast solve times.

I urge the AtCoder admins and community to inspect his submission history for ABC 479 and take necessary action.

atcoder_official read this please.

Title: Cheating Report: Account NGUYENVUHOANG in Codeforces Round 1125 (Div. 3)

Hello everyone,

I am a student from Kon Tum High School for the Gifted in Vietnam and a member of the Vietnam Olympiad in Informatics (VOI) training team. (Note: Since my English is not very good, this blog post was translated and polished with the help of AI.)

I am writing this blog to report account NGUYENVUHOANG for cheating in Codeforces Round 1125 (Div. 3).

Before going into details, I would like to clarify that this post is not driven by personal envy. During internal training contests organized by our school teachers, NGUYENVUHOANG repeatedly used ChatGPT to solve problems. He routinely solved 2500+ rated problems in under 5 minutes with complex code over 100 lines long, despite being only 16 years old. In short, he relies heavily on AI to generate solutions for almost every problem.

Looking closely at his submission timeline in the recent Div. 3 contest: - He solved the first 3 problems (A, B, C) in just 5 to 7 minutes each. - After getting AC on problem E after 20 minutes, he miraculously took only 6 minutes to get AC on problem D, followed immediately by another 6 minutes to get AC on problem F. (It is completely unreasonable to read, fully comprehend, and code a solution for problem F in such a short window). - Although his initial solution for problem H was hacked due to a hash collision, he managed to submit another AC solution 40 minutes later on problem H — a problem that had roughly only 200 ACs on the unofficial leaderboard.

Additional Evidence: - AtCoder Profile: https://atcoder.jp/users/nvhoang I can confidently assert that he cheats on AtCoder as well. Inspecting his submission history reveals structural patterns, variable naming, and coding styles characteristic of AI-generated code with minor manual tweaks.

As someone who values integrity, I cannot stand by and let the reputation of our school's Vietnam Olympiad team be tarnished by dishonest behavior. I hope the Codeforces admins review this submission history and take appropriate action against this account.

MikeMirzayanov geranazavr555 read this blog please.