I submitted a problem yesterday at IST time 23:59(it got accepted by 23:59 also) but the heat map for yesterday is empty(I have submitted a problem after that and it appears in today's heat map). However the my profile statistics correctly shows that I did problems 9 days in a row for the past month. Note that the problem submitted at 23:59 does not show up for either yesterday's or today's heat map.

While practicing from problemset. I often accidentally solve a problem from a contests like Kotlin Heroes. For easier questions, when I find that I can not submit it in C++, I overlook it and move to a different problem. However sometimes the problem is good and gives some nice practice. What approach do you take to check whether your code is correct, in such cases?