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General theoretical results on rectilinear embeddability of graphs. (English) Zbl 0732.05021
Summary: In the design of certain kinds of electronic circuits the following question arises: given a non-negative integer k, what graphs admit of a plane embedding such that every edge is a broken line formed by horizontal and vertical segments and having at most k bends? Any such graph is said to be k-rectilinear. No matter what k is, an obvious necessary condition for k-rectilinearity is that the degree of each vertex does not exceed four.
Our main result is that every planar graph H satisfying this condition is 3-rectilinear: in fact, it is 2-rectilinear with the only exception of the octahedron. We also outline a polynomial-time algorithm which actually constructs a plane embedding of H with at most 2 bends (3 bends if H is the octahedron) on each edge. The resulting embedding has the property that the total number of bends does not exceed 2n, where n is the number of vertices of H.

##### MSC:
 05C10 Planar graphs; geometric and topological aspects of graph theory 94C15 Applications of graph theory to circuits and networks
##### Keywords:
rectilinear embeddability
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##### References:
 [1] Y. Liu, Boolean approach to planar embeddings of a graph,Acta Math. Sinica, New Series,5 (1989), 44–79. · Zbl 0780.05017 [2] R. Tamassia and I. G. Tollis, A Provably Good Linear Algorithm for Embedding Graphs in the Rectilinear Grid, UILU-ENG-85-2233, ACT-64, Coordinated Science Laboratory, Uni. Illinois, 1985.
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