3-Colorability of Pseudo-Triangulations
Oswin Aichholzer, Franz Aurenhammer, Thomas Hackl, Clemens Huemer, Alexander Pilz, Birgit Vogtenhuber · International Journal of Computational Geometry & Applications · 2015
Deciding 3-colorability for general plane graphs is known to be an NP-complete problem. However, for certain families of graphs, like triangulations, polynomial time algorithms exist. We consider the family of pseudo-triangulations, which are a generalization of triangulations, and prove NP-completeness for this class. This result also holds if we bound their face degree to four, or exclusively consider pointed pseudo-triangulations with maximum face degree five. In contrast to these completeness results, we show that pointed pseudo-triangulations with maximum face degree four are always 3-colorable. An according 3-coloring can be found in linear time. Some complexity results relating to the rank of pseudo-triangulations are also given.