False positive thrown by MOSS



Two days ago, I received a mail from Codechef stating that my solution has matched to someone else’s and my ratings will be dropped. Link to the submissions:



They gave me a privilege to write them back if I have not violated any of the rules or the code of conduct. (The mail had a strict warning as well : ***“Please do not write back or approach us if you have violated any of the rules. If you do so, your explanation won’t be considered and we might also block your account without any intimation.”***). I have been penalized in so called case of plagiarism once before also just because I had run my code on ideone and at that time I was not aware of the fact that the codes executed on ideone are public by default. So I didn’t respond to the mail I received last time but this time Since I haven’t done anything wrong, neither knowingly nor unknowingly, So It’s my duty to write for the sake of justice.

So, I replied to the mail but haven’t got any response yet. That’s why I had to write here. First of all let me inform you that I have not violated any of the rules I am supposed to follow. I went through the solution of the second user and I found that yes, the codes are matching as far as the control of flow is concerned but once go through the problem statement of the question and you would see that this is the brute force solution that would come to someone’s mind at first instance. Now it’s just a coincidence that both of codes use set of vector to implement the logic. Now let us have close look to both of the solutions, one can easily find that the style of writing the codes are different and codes have been written by different users.

I would like to bring your attention to a few more points:-

  1. Go through all my recent submissions, you would find that I am using the same template in each code.
  2. I have not run this code on any public platform or ide. I tested the code only on my own system.
  3. I have never ever tried to copy/copied a solution from any public/private forum.
  4. I have not discussed the solution or approach for any problem during the contest with anyone.
  5. I went through the profile of the user ‘pandey__ji’ and I don’t even know to whom does this profile/account belongs.

I would not blame the other user since neither I know him, nor I used any public ide, So there is no chance of plagiarism. In addition to all these facts from my side let me add one more thing:- I went through almost all of the submissions made during the contest for this problem and have saved the links for the solutions which are matching to my solution and if I am asked, I can post the links here but it doesn’t mean all those users and I are indulged in some kind of unethical activity.

This is all I can say to prove my innocence. I would request Codechef to look into this matter and restore my submissions and ratings. And if the informations I have provided or I can provide is not sufficient to prove my innocence then punish me properly and suspend my account permanently.

In hope of a response…


Thank you!

UPD: The issue is resolved now. My account won’t be penalized. Thanks Codechef!


Hello prnjl_rai

I checked my mail today only and I found this plagiarism message. I don’t understand why do they keep such constraints which can be passed using bruteforce code and then they blame us of plagiarism for the same brute forcecode. What I wrote in my code was pure bruteforce and I went through other people’s solution as well. They also did the same thing. It was just an accident that our codes are similar. I’ve written back to them. I hope they look into this matter as early as possible.


It happened to me in august lunchtime. It was simple ad hoc problem and usually for array everyone one takes arr[].
And the template of code is

int n;
int arr[n];
for(int i=0;i<n;i++)

//computation part


Now in computation part the problem is too basic to adopt any other way.So probability is high that it matches with any other and MOSS sense some positive result. I requested the authority a lot via mail but they always reply with pre defined mail structure that it was checked line by line and it could not be like most of your code matches. And we are dropping your ratings. And I had a decent rank of around 200 in that contest.
It brings the morale down when you have to not cheated and are penalised for ratings which takes effort to increase in every contest.


@pandey__ji , The issued is resolved now. My account is restored. I hope yours would have been restored too.


Usually they wont reply. Whatever argument you give over mail is considered, and if valid, your submissions will be restored, else they go ahead with rating penalty.