Problems derive from some competitive programming contests and other places.
- Codeforces (still alive)
- Bestcoder/BZOJ/POJ (old school)
- other online juage platforms
- met in some CTFs (maybe PPC/MISC/RE type)
- Project Euler
- met in the life
But now, here is becoming a playground for me to learn different languages by solving algorithm problems! Especially Go & Rust & Haskell & Kotlin(maybe) <3