Maximum Independent Set on B1-VPG Graphs

We present two approximation algorithms for the maximum independent set (MIS) problem over the class of B-1-VPG graphs and also for the subclass, equilateral B-1-VPG graphs. The first algorithm is shown to have an approximation guarantee of O((log n)(2)) whereas the second one is shown to have an approximation guarantee of O(log d) where d denotes the ratio d(max)/d(min) and d(max) and d(min) denote respectively the maximum and minimum length of of any arm in the input L-representation of the graph. No approximation algorithms have been known for the MIS problem for these graph classes before. Also, the NP-completeness of the decision version restricted to unit length equilateral B-1-VPG graphs is established.