This code was originally authored by a Stackoverflow user dragon-energy (referred to as the author) and posted under following page:
https://stackoverflow.com/questions/41946007/efficient-and-well-explained-implementation-of-a-quadtree-for-2d-collision-det
This post also features an extensive explanation of a QuadTree data structure and selected alternatives, as well as describes the approach taken in this very implementation.
Minor modifications include:
- organization of the code into files,
- float-to-int type change,
- a header addition,
- a bug fix as mentioned by myself in the very same question page linked above.
As for the license, I follow whatever terms original source implies. As the author has kindly noted:
"Oh and feel free to use this code I post however you want, even for commercial projects. I would really love it if people let me know if they find it useful, but do as you wish."
And generally all Stackoverflow-posted code is by default licensed with CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/