Last Update: October 26, 1994
A (vertex) coloring of an undirected graph is an assignment of a label to each node. It is required that the labels on the pair of nodes incident to any edge be different. A minimum coloring of a graph is a coloring that uses as few different labels as possible.
Clique and coloring problems are very closely related. It is straightforward to see that the size of the maximum clique is a lower bound on the minimum number of labels needed to color a graph.
Many problems of practical interest can be modeled as clique and coloring problems. The general form of these applications involves forming a graph with nodes representing items of interest. An edge connects two ``incompatible'' items. The maximum clique problem is then to find as large a set of pairwise incompatible items as possible. The minimum coloring problem is to assign a color to each item so that every incompatible pair is assigned different colors.
This document tries to bring together the various resources that are available on the Internet to help in formulating and solving coloring problems.
This work began with the Second DIMACS Challenge, and many of the items in this report were first collected there. The purpose of this report is to expand on those items and provide a mechanism for further additions to that work.
Last revision: November 3, 1994
This a work in progress, intended as a quick introduction to the clique and coloring problems, not an exhaustive survey. (More complete surveys and bibliographies are listed in the references, some of them available via anonymous FTP from dimacs.rutgers.edu.) Here we restrict our attention to key references (the set of which may change as the document evolves). Feel free to send me any suggested additions or clarifications, or additional project suggestions. The email address for suggestions is trick+@cmu.edu. The Postscript form is also available.