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A matchstick graph is a plane graph with edges drawn as unit distance line segments. This class of graphs was introduced by Harborth who conjectured that a matchstick graph on $n$ vertices can have at most $\lfloor 3n - \sqrt{12n -…

Combinatorics · Mathematics 2025-06-04 Panna Gehér , Géza Tóth

A 1-planar graph is a graph which has a drawing on the plane such that each edge is crossed at most once. If a 1-planar graph is drawn in that way, the drawing is called a {\it 1-plane graph}. A graph is maximal 1-plane (or 1-planar) if no…

Combinatorics · Mathematics 2025-05-01 Zhangdong Ouyang , Yuanqiu Huang , Licheng Zhang , Fengming Dong

A graph is near-planar if it can be obtained from a planar graph by adding an edge. We show the surprising fact that it is NP-hard to compute the crossing number of near-planar graphs. A graph is 1-planar if it has a drawing where every…

Computational Geometry · Computer Science 2012-03-28 Sergio Cabello , Bojan Mohar

We study 3-plane drawings, that is, drawings of graphs in which every edge has at most three crossings. We show how the recently developed Density Formula for topological drawings of graphs (KKKRSU GD 2024) can be used to count the…

Combinatorics · Mathematics 2025-03-12 Miriam Goetze , Michael Hoffmann , Ignaz Rutter , Torsten Ueckerdt

We introduce and study embeddings of graphs in finite projective planes, and present related results for some families of graphs including complete graphs and complete bipartite graphs. We also make connections between embeddings of graphs…

Combinatorics · Mathematics 2013-10-02 Keith Mellinger , Ryan Vaughn , Oscar Vega

It is shown that every $n$-vertex graph that admits a 2-bend RAC drawing in the plane, where the edges are polylines with two bends per edge and any pair of edges can only cross at a right angle, has at most $20n-24$ edges for $n\geq 3$.…

Discrete Mathematics · Computer Science 2024-11-05 Csaba D. Tóth

We prove that the geometric thickness of graphs whose maximum degree is no more than four is two. All of our algorithms run in O(n) time, where n is the number of vertices in the graph. In our proofs, we present an embedding algorithm for…

Computational Geometry · Computer Science 2007-05-23 Christian A. Duncan , David Eppstein , Stephen G. Kobourov

A graph is NIC-planar if it admits a drawing in the plane with at most one crossing per edge and such that two pairs of crossing edges share at most one common end vertex. NIC-planarity generalizes IC-planarity, which allows a vertex to be…

Discrete Mathematics · Computer Science 2017-11-06 Christian Bachmaier , Franz J. Brandenburg , Kathrin Hanauer , Daniel Neuwirth , Josef Reislhuber

A shape visibility representation displays a graph so that each vertex is represented by an orthogonal polygon of a particular shape and for each edge there is a horizontal or vertical line of sight between the polygons assigned to its…

Computational Geometry · Computer Science 2018-01-25 Franz J. Brandenburg

A graph is 1-planar if it can be drawn in the plane so that each edge is crossed at most once. However, there are 1-planar graphs which do not admit a straight-line 1-planar drawing. We show that every 1-planar graph has a straight-line…

Computational Geometry · Computer Science 2021-09-07 Franz J. Brandenburg

An outer-1-planar graph is a graph admitting a drawing in the plane so that all vertices appear in the outer region of the drawing and every edge crosses at most one other edge. This paper establishes the local structure of outer-1-planar…

Combinatorics · Mathematics 2023-06-22 Yan Li , Xin Zhang

A graph is 1-planar if it can be drawn on the plane so that each edge is crossed by at most one other edge. In this note we give examples of class two 1-planar graphs with maximum degree six or seven.

Combinatorics · Mathematics 2011-04-26 Xin Zhang

Define a boundary point of a graph which is embedded in the Euclidean plane a vertex which is incident to only one edge. In this paper we consider graphs which are embedded in the Euclidean plane with a finite number of boundary points. The…

Combinatorics · Mathematics 2015-01-12 Yashar Memarian

In a \emph{fan-planar drawing} of a graph an edge can cross only edges with a common end-vertex. Fan-planar drawings have been recently introduced by Kaufmann and Ueckerdt, who proved that every $n$-vertex fan-planar drawing has at most…

Computational Geometry · Computer Science 2019-09-04 Carla Binucci , Emilio Di Giacomo , Walter Didimo , Fabrizio Montecchiani , Maurizio Patrignani , Ioannis G. Tollis

We consider embeddings of planar graphs in $R^2$ where vertices map to points and edges map to polylines. We refer to such an embedding as a polyline drawing, and ask how few bends are required to form such a drawing for an arbitrary planar…

Computational Geometry · Computer Science 2014-06-17 Taylor Gordon

We study biplane graphs drawn on a finite planar point set $S$ in general position. This is the family of geometric graphs whose vertex set is $S$ and can be decomposed into two plane graphs. We show that two maximal biplane graphs---in the…

Computational Geometry · Computer Science 2017-08-10 Alfredo García , Ferran Hurtado , Matias Korman , Inês Matos , Maria Saumell , Rodrigo I. Silveira , Javier Tejel , Csaba D. Tóth

We explore various techniques for counting the number of straight-edge crossing-free graphs that can be embedded on a planar point set. In particular, we derive a lower bound on the ratio of the number of such graphs with $m+1$ edges to the…

Combinatorics · Mathematics 2019-05-24 Siddharth Prasad

We prove that every 1-planar graph G has a z-parallel visibility representation, i.e., a 3D visibility representation in which the vertices are isothetic disjoint rectangles parallel to the xy-plane, and the edges are unobstructed…

Computational Geometry · Computer Science 2017-08-22 Patrizio Angelini , Michael A. Bekos , Michael Kaufmann , Fabrizio Montecchiani

Recently, there has been interest in representing single graphs by multiple drawings; for example, using graph stories, storyplans, or uncrossed collections. In this paper, we apply this idea to orthogonal graph drawing. Due to the…

A graph whose vertices are points in the plane and whose edges are noncrossing straight-line segments of unit length is called a \emph{matchstick graph}. We prove two somewhat counterintuitive results concerning the maximum number of edges…

Combinatorics · Mathematics 2025-06-03 Panna Gehér , János Pach , Konrad Swanepoel , Géza Tóth