Let me mention one of the main contributor named Nitin nitin_05 Singh Rawat.
Most important tip
Codeforces Round #748 (Div. 3)
Solution B
Solution C
Solution D1
Solution D2
Solution E
Not only Codeforces Round #748 (Div. 3), every contest in his profile, he uses the same way to contribute to code forces and take "ratings" in return.
If anyone wanted to learn how to add comments in code, contact nitin_05.
MikeMirzayanov have a look at his abilities, how beautifully he adds comments in his code.