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There is a graph reduction system so that every optimal 1-planar graph can be reduced to an irreducible extended wheel graph, provided the reductions are applied such that the given graph class is preserved. A graph is optimal 1-planar if…

Computational Geometry · Computer Science 2016-10-28 Franz J. Brandenburg

A straight-line drawing $\delta$ of a planar graph $G$ need not be plane, but can be made so by \emph{untangling} it, that is, by moving some of the vertices of $G$. Let shift$(G,\delta)$ denote the minimum number of vertices that need to…

Computational Geometry · Computer Science 2009-01-27 Xavier Goaoc , Jan Kratochvil , Yoshio Okamoto , Chan-Su Shin , Andreas Spillner , Alexander Wolff

The problem of deciding whether a biconnected planar digraph $G=(V,E)$ can be augmented to become an $st$-planar graph by adding a set of oriented edges $E' \subseteq V \times V$ is known to be NP-complete. We show that the problem is…

Data Structures and Algorithms · Computer Science 2023-09-28 Liana Khazaliya , Philipp Kindermann , Giuseppe Liotta , Fabrizio Montecchiani , Kirill Simonov

A graph is $1$-$planar$ if it can be drawn in the plane so that each edge is crossed by at most one other edge. Moreover, a 1-planar graph $G$ is $optimal$ if it satisfies $|E(G)|=4|V(G)|-8$. J. Fujisawa et al. [16] first considered…

Combinatorics · Mathematics 2022-05-25 Jiangyue Zhang , Yan Wu , Heping Zhang

The Planar Contraction problem is to test whether a given graph can be made planar by using at most k edge contractions. This problem is known to be NP-complete. We show that it is fixed-parameter tractable when parameterized by k.

Data Structures and Algorithms · Computer Science 2012-04-24 Petr A. Golovach , Pim van 't Hof , Daniel Paulusma

A visualized graph is a powerful tool for data analysis and synthesis tasks. In this case, the task of visualization constitutes not only in displaying vertices and edges according to the graph representation, but also in ensuring that the…

Combinatorics · Mathematics 2024-08-01 Sergey Kurapov , Maxim Davidovsky

Covering problems are fundamental classical problems in optimization, computer science and complexity theory. Typically an input to these problems is a family of sets over a finite universe and the goal is to cover the elements of the…

Data Structures and Algorithms · Computer Science 2008-02-14 Omid Amini , Fedor V. Fomin , Saket Saurabh

Subgraph counting is a fundamental and well-studied problem whose computational complexity is well understood. Quite surprisingly, the hypergraph version of subgraph counting has been almost ignored. In this work, we address this gap by…

Computational Complexity · Computer Science 2025-06-18 Marco Bressan , Julian Brinkmann , Holger Dell , Marc Roth , Philip Wellnitz

A graph is $1$-planar if it has a drawing in the plane such that each edge is crossed at most once by another edge. Moreover, if this drawing has the additional property that for each crossing of two edges the end vertices of these edges…

Combinatorics · Mathematics 2020-01-27 Igor Fabrici , Jochen Harant , Tomáš Madaras , Samuel Mohr , Roman Soták , Carol T. Zamfirescu

Topological drawings are natural representations of graphs in the plane, where vertices are represented by points, and edges by curves connecting the points. Topological drawings of complete graphs and of complete bipartite graphs have been…

Computational Geometry · Computer Science 2017-02-10 Jean Cardinal , Stefan Felsner

Computing planar orthogonal drawings with the minimum number of bends is one of the most relevant topics in Graph Drawing. The problem is known to be NP-hard, even when we want to test the existence of a rectilinear planar drawing, i.e., an…

Computational Geometry · Computer Science 2023-09-07 Emilio Di Giacomo , Walter Didimo , Giuseppe Liotta , Fabrizio Montecchiani , Giacomo Ortali

Recently, a new way of avoiding crossings in straight-line drawings of non-planar graphs has been investigated. The idea of partial edge drawings (PED) is to drop the middle part of edges and rely on the remaining edge parts called stubs.…

We consider upward-planar layered drawings of directed graphs, i.e., crossing-free drawings in which each edge is drawn as a y-monotone curve going upward from its tail to its head, and the y-coordinates of the vertices are integers. The…

Computational Geometry · Computer Science 2026-05-04 Patrizio Angelini , Sabine Cornelsen , Giordano Da Lozzo , Fabrizio Frati , Philipp Kindermann , Ignaz Rutter , Johannes Zink

Let $G$ be a simple topological graph and let $\Gamma$ be a polyline drawing of $G$. We say that $\Gamma$ \emph{partially preserves the topology} of $G$ if it has the same external boundary, the same rotation system, and the same set of…

Computational Geometry · Computer Science 2018-09-24 Emilio Di Giacomo , Peter Eades , Giuseppe Liotta , Henk Meijer , Fabrizio Montecchiani

Covering and partitioning the edges of a graph into cliques are classical problems at the intersection of combinatorial optimization and graph theory, having been studied through a range of algorithmic and complexity-theoretic lenses.…

Data Structures and Algorithms · Computer Science 2025-06-27 Fedor V. Fomin , Petr A. Golovach , Danil Sagunov , Kirill Simonov

In this paper, we give polynomial-time algorithms that can take a graph G with a given combinatorial embedding on an orientable surface S of genus g and produce a planar drawing of G in R^2, with a bounding face defined by a polygonal…

Computational Geometry · Computer Science 2009-08-13 Christian A. Duncan , Michael T. Goodrich , Stephen G. Kobourov

We study the problem of embedding graphs in the plane as good geometric spanners. That is, for a graph $G$, the goal is to construct a straight-line drawing $\Gamma$ of $G$ in the plane such that, for any two vertices $u$ and $v$ of $G$,…

Data Structures and Algorithms · Computer Science 2020-02-14 Oswin Aichholzer , Manuel Borrazzo , Prosenjit Bose , Jean Cardinal , Fabrizio Frati , Pat Morin , Birgit Vogtenhuber

Motivated by hybrid graph representations, we introduce and study the following beyond-planarity problem, which we call $h$-Clique2Path Planarity: Given a graph $G$, whose vertices are partitioned into subsets of size at most $h$, each…

Data Structures and Algorithms · Computer Science 2018-08-29 Patrizio Angelini , Peter Eades , Seok-Hee Hong , Karsten Klein , Stephen Kobourov , Giuseppe Liotta , Alfredo Navarra , Alessandra Tappini

Given a hypergraph $H$, the Planar Support problem asks whether there is a planar graph $G$ on the same vertex set as $H$ such that each hyperedge induces a connected subgraph of $G$. Planar Support is motivated by applications in graph…

Discrete Mathematics · Computer Science 2015-07-10 René van Bevern , Iyad Kanj , Christian Komusiewicz , Rolf Niedermeier , Manuel Sorge

A graph $G=(V,E)$ is called 1-planar if it admits a drawing in the plane such that each edge is crossed at most once. In this paper, we study bipartite $1$-planar graphs with prescribed numbers of vertices in partite sets. Bipartite…

Combinatorics · Mathematics 2015-03-05 Július Czap , Jakub Przybyło , Erika Škrabuľáková