Determine if point is inside polygon

Hello!
Maybe it will be more clear, if I try to explain it with image:


So, the question is, what kind of algorithm can be used to determine, is certain point inside of polygon or not. By saying "inside of polygon" I mean the point 1. And, respectively, points 2 and 3 are not inside of it.

The issue names no repository files, tests, or entry points. First clarify whether this should become an implemented repository feature or only a topic suggestion, then define the expected polygon and point inputs and acceptance criteria for boundary cases. No implementation location or test command is provided.

索引モデルが issue の本文から書いたものです。