Comment by qsort
We are talking past each other here.
Once I solved an Advent of Code problem, I felt like the problem wasn't general enough, so I solved the more general version as well. I like programming to the point of doing imaginary homework, then writing myself some extra credit and doing that as well. Way too much for my own good.
The point is that solving a new problem is interesting. Solving a problem you already know exactly how to solve isn't interesting and isn't even intellectual exercise. I would gain approximately zero from writing a new hash table from scratch whenever I needed one instead of just using std::map.
Problem solving absolutely is a muscle and it's use it or lose it, but you don't train problem solving by solving the same problem over and over.
> Solving a problem you already know exactly how to solve isn't interesting and isn't even intellectual exercise.
That isn't typically what my programming tasks at work consist of. A large part of the work is coming up with what exactly needs to be done, given the existing code and constraints imposed by technical and domain circumstances, and iterating over that. Meaning, this intellectual work isn't detached from the existing code, or from constraints imposed by the language, libraries and tooling. Hence an important part of the intellectual challenges are tied to actually developing and integrating the code yourself. Maybe you don't find those interesting, but they aren't problems one "already knows exactly how to solve". The solution, instead, is the result of a discovery and exploration process.