I have a complain. I have solve Question B & C of Codeforces Round 931 & it was succesfully run in pretests, but after the contest it's showing runtime error. & submitting the same code after the contest it is succesfully accepted. Please tell me how it's happened. harsh__h

C: During Contest & after contest

B: During Contest & after contest

[Later Edited]: I have got the problem that it's due to vector size declaration of 30, but i am confused why it didn't give runtime error on test 1 instead of this later cases.

Why does rolling back of rating frequently happen nowadays? Is it due to plag detection of several participants? Does CF returns previous rating or there is any possiblities of rating change?