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An ortho-polygon visibility representation $\Gamma$ of a $1$-plane graph $G$ (OPVR of $G$) is an embedding preserving drawing that maps each vertex of $G$ to a distinct orthogonal polygon and each edge of $G$ to a vertical or horizontal…

Data Structures and Algorithms · Computer Science 2018-08-03 Giuseppe Liotta , Fabrizio Montecchiani , Alessandra Tappini

A set $V$ is said to be separated by subsets $V_1,\ldots,V_k$ if, for every pair of distinct elements of $V$, there is a set $V_i$ that contains exactly one of them. Imposing structural constraints on the separating subsets is often…

Combinatorics · Mathematics 2024-08-06 Lyuben Lichev , Nicolás Sanhueza-Matamala

A temporal graph $G$ is a sequence $(G_t)_{t \in I}$ of graphs on the same vertex set of size $n$. The \emph{temporal exploration problem} asks for the length of the shortest sequence of vertices that starts at a given vertex, visits every…

Data Structures and Algorithms · Computer Science 2025-12-01 Paul Bastide , Carla Groenland , Lukas Michel , Clément Rambaud

A topological graph is a graph drawn in the plane. A topological graph is $k$-plane, $k>0$, if each edge is crossed at most $k$ times. We study the problem of partitioning the edges of a $k$-plane graph such that each partite set forms a…

For an undirected $n$-vertex graph $G$ with non-negative edge-weights, we consider the following type of query: given two vertices $s$ and $t$ in $G$, what is the weight of a minimum $st$-cut in $G$? We solve this problem in preprocessing…

Computational Geometry · Computer Science 2015-12-24 Glencora Borradaile , David Eppstein , Amir Nayyeri , Christian Wulff-Nilsen

A graph $G=(V,E)$ is a support of a hypergraph $H=(V,S)$ if every hyperedge induces a connected subgraph in $G$. Supports are used for certain types of hypergraph visualizations. In this paper we consider visualizing spatial hypergraphs,…

Computational Geometry · Computer Science 2018-08-30 Thom Castermans , Mereke van Garderen , Wouter Meulemans , Martin Nöllenburg , Xiaoru Yuan

A ladder is a $2 \times k$ grid graph. When does a graph class $\mathcal{C}$ exclude some ladder as a minor? We show that this is the case if and only if all graphs $G$ in $\mathcal{C}$ admit a proper vertex coloring with a bounded number…

Combinatorics · Mathematics 2022-10-19 Tony Huynh , Gwenaël Joret , Piotr Micek , Michał T. Seweryn , Paul Wollan

The power graph of a group $G$ is the graph whose vertex set is $G$ and two distinct vertices are adjacent if one is a power of the other. In this paper, the minimum degree of power graphs of certain classes of cyclic groups, abelian…

Combinatorics · Mathematics 2017-05-12 Ramesh Prasad Panda , K. V. Krishna

Graph connectivity is a fundamental combinatorial optimization problem that arises in many practical applications, where usually a spanning subgraph of a network is used for its operation. However, in the real world, links may fail…

Data Structures and Algorithms · Computer Science 2022-09-13 Dimitris Fotakis , Evangelia Gergatsouli , Charilaos Pipis , Miltiadis Stouras , Christos Tzamos

In this paper we show how to combine two algorithmic techniques to obtain linear time algorithms for various optimization problems on graphs, and present a subroutine which will be useful in doing so. The first technique is iterative…

Data Structures and Algorithms · Computer Science 2015-09-28 Ken-ichi Kawarabayashi , Zhentao Li , Bruce Reed

A planar graph is essentially $4$-connected if it is 3-connected and every of its 3-separators is the neighborhood of a single vertex. Jackson and Wormald proved that every essentially 4-connected planar graph $G$ on $n$ vertices contains a…

Combinatorics · Mathematics 2019-12-09 Igor Fabrici , Jochen Harant , Samuel Mohr , Jens M. Schmidt

A set $S$ of isometric paths of a graph $G$ is ``$v$-rooted'', where $v$ is a vertex of $G$, if $v$ is one of the endpoints of all the isometric paths in $S$. The isometric path complexity of a graph $G$, denoted by $ipco{G}$, is the…

Combinatorics · Mathematics 2025-09-03 Dibyayan Chakraborty , Jérémie Chalopin , Florent Foucaud , Yann Vaxès

Quantum circuits composed of CNOT and $R_z$ are fundamental building blocks of many quantum algorithms, so optimizing the synthesis of such quantum circuits is crucial. We address this problem from a theoretical perspective by studying the…

Quantum Physics · Physics 2025-09-15 Yixin Cao , Yiren Lu , Junhong Nie , Xiaoming Sun , Guojing Tian

In this paper, we study the outerplanarity of planar graphs, i.e., the number of times that we must (in a planar embedding that we can initially freely choose) remove the outerface vertices until the graph is empty. It is well-known that…

Data Structures and Algorithms · Computer Science 2024-07-08 Therese Biedl , Debajyoti Mondal

For a given graph $H$, a graph $G$ is $H$-linked if, for every injection $\varphi: V(H) \to V(G)$, the graph $G$ contains a subdivision of $H$ with $\varphi(v)$ corresponding to $v$, for each $v\in V(H)$. Let $f(H)$ be the minimum integer…

Combinatorics · Mathematics 2019-12-09 Chris Stephens , Dong Ye

A vertex of degree one in a tree is called an end vertex and a vertex of degree at least three is called a branch vertex. For a graph $G$, let $\sigma_2$ be the minimum degree sum of two nonadjacent vertices in $G$. We consider tree…

Combinatorics · Mathematics 2015-05-19 Zhora Nikoghosyan

A $3$-connected graph $G$ is essentially $4$-connected if, for any $3$-cut $S\subseteq V(G)$ of $G$, at most one component of $G-S$ contains at least two vertices. We prove that every essentially $4$-connected maximal planar graph $G$ on…

Combinatorics · Mathematics 2021-01-28 Igor Fabrici , Jochen Harant , Samuel Mohr , Jens M. Schmidt

We consider the task of drawing a graph on multiple horizontal layers, where each node is assigned a layer, and each edge connects nodes of different layers. Known algorithms determine the orders of nodes on each layer to minimize crossings…

Data Structures and Algorithms · Computer Science 2025-03-03 Alexander Dobler , Jakob Roithinger

A matching is a set of edges without common endpoint. It was recently shown that every 1-planar graph (i.e., a graph that can be drawn in the plane with at most one crossing per edge) that has minimum degree 3 has a matching of size at…

Computational Geometry · Computer Science 2020-03-19 Therese Biedl , Fabian Klute

An edge subset \( S \subseteq E(G) \) is called a 3-restricted edge-cut if $G-S$ is disconnected and each component of \( G - S \) contains at least three vertices. The 3-restricted edge-connectivity of a graph \( G \), denoted by \(…

Combinatorics · Mathematics 2026-04-14 Wenxin Wang , Yingzhi Tian , Jing Wang