We provide an algorithm for computing a planar morph between any two planar straight-line drawings of any n-vertex plane graph in O(n) morphing steps, thus improving upon the previously best known O(n) upper bound. Further, we prove that our algorithm is optimal, that is, we show that there exist two planar straight-line drawings Γs and Γt of an n-vertex plane graph G such that any planar morph...

In this paper, we extend the Grr otzsch Theorem by proving that the clique hypergraph H(G) of every planar graph is 3-colorable. We also extend this result to list colorings by proving that H(G) is 4-choosable for every planar or projective planar graph G. Finally, 4-choosability of H(G) is established for the class of locally planar graphs on arbitrary surfaces.

We investigate the supereulerian graph problems within planar graphs, and we prove that if a 2-edge-connected planar graph G is at most three edges short of having two edge-disjoint spanning trees, then G is supereulerian except a few classes of graphs. This is applied to show the existence of spanning Eulerian subgraphs in planar graphs with small edge cut conditions. We also determine several...

A graph is said to be planar if it can be drawn on the plane in such a way that no two of its edges cross. Given a graph G = (V,E) with vertex set V and edge set E, the objective of graph planarization is to find a minimum cardinality subset of edges F ⊆ E such that the graph G = (V,E \ F ), resulting from the removal of the edges in F from G, is planar. This problem is also known as the maximu...

Given a graphG, a total k-coloring ofG is a simultaneous coloring of the vertices and edges ofGwith at most k colors. If ∆(G) is themaximum degree ofG, then no graph has a total ∆-coloring, but Vizing conjectured that every graph has a total (∆ + 2)-coloring. This Total Coloring Conjecture remains open even for planar graphs. This article proves one of the two remaining planar cases, showing th...

If G is a plane graph and x, y ∈ V (G), then the dual distance of x and y is equal to the minimum number of crossings of G with a closed curve in the plane joining x and y. Riskin [7] proved that if G0 is a 3connected cubic planar graph, and x, y are its vertices at dual distance d, then the crossing number of the graph G0 + xy is equal to d. Riskin asked if his result holds for arbitrary 3-con...

We present an n-processor and O(lo~n)-time parallel RAM algorithm for finding a depth-first-search tree in an n·vertex planar graph. The algorithm is based on a new n-processor algorithm for finding a cyclic separator in a planar graph and Smith's original parallel depth-first-search algorithm for planar graphs [Smi86].

It is well-known that every planar or projective planar graph can be 3-colored so that each color class induces a forest. This bound is sharp. In this paper, we show that there are in fact exponentially many 3-colorings of this kind for any (projective) planar graph. The same result holds in the setting of 3-list-colorings.

The depth of a planar embedding is a measure of the topological nesting of the biconnected components of the graph. Minimizing the depth of planar embeddings has important practical applications to graph drawing. We give a linear time algorithm for computing a minimum depth embedding of a planar graphs whose biconnected components have a prescribed embedding.

We shall prove that a connected graph G is projective-planar if and only if it has a 2n-fold planar connected covering obtained as a composition of an n-fold covering and a double covering for some n¿ 1 and show that every planar regular covering of a nonplanar graph is such a composite covering. c © 2002 Elsevier Science B.V. All rights reserved.