The Two-Guard Polygon Walk Problem

摘要

Consider a simple polygon. A walk is conducted by two guards on the polygon boundary. They start at a boundary point and walk on the boundary. It is required that the two guards maintain their mutual visibility at all times and eventually meet together again. A polygon may or may not be walkable, depending on where the two guards start their walk or no matter where they start on the boundary. In this work, we characterize the class of walkable polygons by two guards by presenting a set of forbidden patterns.