Update on 8/18/2026: yql0991666 have cheated to become a Master. How can he still not be banned?

Update: Congratulations to yql0991666, the CHEATER is disabled! Good job, Mike!

I, BitByBit123, suspect that yql0991666 is a cheater. I would like to report some suspicious behaviors and request an investigation.

Update on 8/18/2026

yql0991666, could you explain 387437964 387437988 how can you write 1.6KB code in 3 seconds?

Looking at the code for Problem E, what kind of person would write such a long definition on a single line (the fourth line)?

If you interpret this as a way to make the code more compact (by consolidating lines), then why are the assignment statements on lines 19 through 24 separated?

The only explanation is that the AI-generated code was partially modified.

Also yql0991666 you didn't solve problem D because you allocated an array smaller than required, Even when there's a notification saying the data range changed. The only explanation is that yql0991666 can't read English and copied the wrong statement to ChatGPT.

And yql0991666 you use indention with a tab size 4 before but 8 now, WHY??

Also lets check out his weird code.

Suspicious contest behavior

As shown above, yql0991666 solved multiple problems in an unusually short period of time and in an unusual order. Some other examples:

https://codeforces.me/contest/2252/submission/385960817

https://codeforces.me/contest/2252/submission/385961550

During contests, the user submitted multiple accepted solutions for the same problem, where the only visible changes were formatting-related (such as spaces or indentation).

AI-like code style and inconsistent coding habits

Examples:

https://codeforces.me/contest/2253/submission/386124818

https://codeforces.me/contest/2248/submission/385185432

https://codeforces.me/contest/2252/submission/385961550

Some submissions contain coding patterns that are commonly seen in AI-generated code, for example:

if(cin>>T)
{
    while(T--)
    {
        /* ... */
    }
}

and:

if(!(cin>>n))return 0;

These patterns appear in some of the user's submissions but not in others, indicating a significant inconsistency in coding style.

Additional inconsistencies include:

• Mixing int* and int[] styles in function parameters.
• Mixing spaces and tabs for indentation.

Examples:

https://codeforces.me/contest/2253/submission/386124818

https://codeforces.me/contest/2253/submission/386109857

https://codeforces.me/contest/2253/submission/386124802

I understand that coding style alone cannot prove cheating, but these changes may indicate that some submissions were not written in the user's usual style.

Inconsistent performance

yql0991666 previously had performances around the 10000+ rank range, but recently achieved several extremely high placements, including top 50 finishes, with a rapid rating increase.

Relevant information:

The improvement appears to be significantly inconsistent with the user's previous competitive programming history.

Additionally, according to publicly available records, yql0991666 scored 100 points in CSP-J2024 and 130 points in CSP-J2025. These results suggest that he can hardly solve problems with difficulty higher than *800 or *1000, which appears inconsistent with the user's recent Codeforces performance.

Source:

Additional information

I personally know this user, Yin Qilong, from the Chinese OI community. There have been previous controversies involving this user, including alleged cheating and harassment on other platforms such as Luogu.

I understand that these points alone may not conclusively prove cheating, so I would appreciate it if Codeforces staff could review the account and related submissions.

(By the way, it has been a long time since the last rollback and there're a lot of cheaters in the latest contests, so could we have a rollback?)