### nihal_47's blog

By nihal_47, history, 7 weeks ago, ,

In the ongoing hacking phase of Educational Codeforces Round 75 I have caught people red handed hacking their solutions of their own fake accounts . What they will do is put something nonsense like this on top of their accepted code : if(string=="dfdfdf34") print("12")

One can easily hack this solution by providing a test case like: 1 dfdfdf34

Like I caught this guy https://codeforces.com/profile/Amr_Abdelazim01

https://codeforces.com/profile/amr_abdelazim Both of these accounts are owned by 1 person and the guy hacked using the method I explained above like 12 times. And this is not the end https://codeforces.com/contest/1251/submission/63335128

https://codeforces.com/contest/1251/submission/63316807

https://codeforces.com/contest/1251/submission/63342216

https://codeforces.com/contest/1251/submission/63341635

https://codeforces.com/contest/1251/submission/63344050 And there many more like this . The person who hacked such solutions is probably the culprit. Admin please look into the issue people like these are ruining the platform badly. God people will do anything for the rating.

• +21

 » 7 weeks ago, # |   +24 Hacks don't help you increase rating in Educational Rounds.
•  » » 6 weeks ago, # ^ |   0 yup but who knows for how long they have been doing this in other contests where hacks does increase rating . Maybe they are unaware that hacks doesn't increase rating in educational rounds.
•  » » » 6 weeks ago, # ^ |   +14 In other contests, where hacking gets you points, participants are divided into rooms, one can only hack in one's own room, so both of these accounts of such person have to be in the same room, hence chances of such cases in other contests is very low.
•  » » » » 6 weeks ago, # ^ |   +4 How many fake accounts one should make to ensure 99% probability that atleast two of his accounts are in the same room?credit: Birthday Paradoxjust kidding:)
•  » » » 6 weeks ago, # ^ |   +2 That is much more difficult, as hacking in normal rounds is only possible in rooms, and the rooms are made randomly. So it unlikely that the fake account and real both are in the same room.However, this is still unethical.
 » 6 weeks ago, # |   0 Idea: it's possible for codeforces to implement some code coverage check system, so if a specific line of code is not reached in the main test but is reached in a hack, then it's likely that either the main test is not strong enough that it missed a whole case in the solution, or the hack exploits an intentional bug in the solution. (however this will make the judge slower, so only run it in case of doubt)Of course, this doesn't completely prevent solutions that intentionally contain bugs, as it's possible to write for example std::cout << ("x" + (n != 123456)) which only prints x when n == 123456, but the line is always reachable.