Ask HN: Professional Implementations of Algorithms

You can take a look at the pathfinding of e.g. warzone2100 (https://github.com/Warzone2100/warzone2100/blob/master/src/f..., battle for wesnoth (https://wiki.wesnoth.org/LuaAPI/wesnoth/paths) or 0ad (https://github.com/0ad/0ad/blob/master/source/simulation2/he...)

Skiena's "Algorithm Design Manual" (which recently got a third edition) introduces algos and their application -- when to use them, why you might use one over another, etc. With lengthy "stories from the trenches" about problems he's solved using them, in some cases. And it's a handy reference on the ideas behind the algos, too

Thanks, I'll take a look at it. I am looking more for code on github, for example.

GNU C++ Standard Library:

https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-...

Things are modified in practice. You need to read the kernel source code, and things like MySQL and Postgres. File systems are all about btrees.