None of these answers are supposed to be clever or the most efficient. They are simply what got me the correct answers for the advent of code problems in 2021.
In fact, I would say some of the answers are written in such a way that the intention is clear so there is no confusion. I try to use modern C++ features that I know about (including C++20 features), but beyond that it is standard C++.
Yes I know you should avoid using namespace std. These are short programs for problems with well defined parameters.