# William J. Lenhart

• FOCS
• 1997
A grid graph is a nite node-induced subgraph of the innnite two-dimensional integer grid. A solid grid graph is a grid graph without holes. For general grid graphs, the Hamiltonian cycle problem is known to be NP-complete. We give a polynomial-time algorithm for the Hamiltonian cycle problem in solid grid graphs, resolving a longstanding open question posed(More)
The link center of a simple polygon P is the set of points x inside P at which the maximal link-distance from x to any other point in P is minimized, where the link distance between two points x, y inside P is defined as the smallest number of straight edges in a polygonal path inside P connecting x to y. We prove several geometric properties of the link(More)
• Graph Drawing
• 1994
This paper examines an innnite family of proximity drawings of graphs called open and closed-drawings, rst deened by Kirkpatrick and Radke 15, 21] in the context of computational morphology. Such proximity drawings include as special cases the well-known Gabriel, relative neighborhood and strip drawings. Complete characterizations of those trees that admit(More)
• Algorithmica
• 1996
Complete characterizations are given for those trees that can be drawn as either the relative neighborhood graph, relatively closest graph, Gabriel graph, or modified Gabriel graph of a set of points in the plane. The characterizations give rise to linear-time algorithms for determining whether a tree has such a drawing; if such a drawing exists one can be(More)
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• J. Comb. Theory, Ser. B
• 1990
We show that there are, up to a trivial equivalence, precisely six theorems of the following form: If the vertices of a graph G are coloured red and white in such a way that no chordless path with four vertices is coloured in certain ways (specified by the particular theorem), then G is perfect if and only if each of the two subgraphs of G induced by all(More)
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