Simplified O(n) algorithms for planar graph embedding, Kuratowski subgraph isolation, and related problems
Date
2018-08-16
Authors
Boyer, John M.
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Abstract
A graph is planar if it can be drawn on the plane with vertices at unique locations
and no edge intersections. Due to the wealth of interest from the computer science
community, there are a number of remarkable but complex O(n) planar embedding algorithms.
This dissertation presents a new method for O(n) planar graph embedding
which avoids some of the complexities of previous approaches. The PC-tree method
of Shih and Hsu has similarities to our algorithm, but the formulation is incorrect
and not O(n) for reasons discussed in this dissertation. Our planarity algorithm operates
directly on an adjacency list representation of a collection of planar biconnected
components, adding one edge at a time to the embedding until the entire graph is
embedded or until a non-planarity condition arises. If the graph is not planar, a new
O(n) algorithm is presented that simplifies the extraction of a Kuratowski subgraph
(a subgraph homeomorphic to [special characters omitted]). The results are then extended to outerplanar
graphs, which are planar graphs that can be embedded with every vertex along
the external face. In linear time, the algorithms find an outerplanar embedding or a
minimal obstructing subgraph homeomorphic to [special characters omitted]. Finally, modifications
to the outerplanarity and planarity obstruction isolators are presented, resulting in
O(n) methods for identifying a subgraph homeomorphic to [special characters omitted].
Description
Keywords
Graph theory, Algorithms