Contests
3 guides
Your first Codeforces contest
Which round to enter, how it’s scored, how to spend the two hours and what happens to your rating.
Upsolve after every contest
The problems you missed in a contest are the best practice you’ll get all week. Try them again within a day, then read the editorial and write the code yourself.
Find the failing case with a stress test
When a solution gets Wrong answer and the samples pass, compare it against a brute force on thousands of small random inputs.