Note on an art gallery problem
György Csizmadia, Gézá Tóth · Computational Geometry · 1998
It is proved that for n > 3, ⌈25(n − 3)⌉ guards are enough to monitor any simply connected art gallery room of n sides if they are stationed at fixed points and their range of vision is 180°. Furthermore, the position of the guards can be determined by an O(n)-time algorithm.