Graph Theory and Combinatorics: Theory and Applications

A special issue of Axioms (ISSN 2075-1680).

Deadline for manuscript submissions: 30 October 2025 | Viewed by 3572

Special Issue Editors

Department of Mathematics, University of Scranton, Scranton, PA 18510, USA
Interests: graph theory; combinatorics

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Guest Editor
Department of Mathematics, University of Hartford, West Hartford, CT 06117, USA
Interests: Graph Theory; Topological Graph Theory

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Guest Editor
Center for Combinatorics, Nankai University, Tianjin 300071, China
Interests: graph theory and its applications; combinatorial optimizations; algorithms and complexity analysis; NP-hard problems; discrete mathematics and its applications in computer science, chemistry, biology, etc.
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Special Issue Information

Dear Colleagues,

Graph theory and combinatorics study discrete structures and their properties. Graph theory focuses on graphs, which are composed of vertices and edges, analyzing connectivity and structural patterns. Combinatorics deals with the counting, arrangements and combinations of discrete objects. Together, these fields provide essential tools for solving problems across diverse disciplines such as computer science, biology and optimization by analyzing relationships and developing efficient algorithms. Recently, there has been significant research activity in both graph theory and combinatorics, spanning theoretical advancements and practical applications.

We are pleased to announce a Special Issue dedicated to graph theory and combinatorics. We invite the submissions of original research articles, reviews and innovative applications within these fields. Manuscripts offering novel insights, methodologies or applications that contribute to advancing the understanding and application of graph theory and combinatorics are welcome.

Dr. Murong Xu
Dr. Jian-Bing Liu
Prof. Dr. Xueliang Li
Guest Editors

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Keywords

  • graph theory
  • combinatorial optimization
  • digraphs
  • hypergraphs
  • connectivity
  • group connectivity
  • strongly group connectivity
  • strong arc connectivity
  • extremal problems
  • extremal digraphs
  • graph coloring
  • list coloring
  • planar graphs
  • nowhere-zero flows
  • edge coloring
  • strong edge coloring
  • chromatic number
  • decomposition
  • eigenvalues
  • supereulerian graphs
  • domination number

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Published Papers (5 papers)

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Research

19 pages, 643 KB  
Article
MaxSum Spanning Tree Interdiction and Improvement Problems Under Weighted l Norm+
by Qiao Zhang, Junhua Jia and Xiao Li
Axioms 2025, 14(9), 691; https://doi.org/10.3390/axioms14090691 - 11 Sep 2025
Abstract
The Max+Sum Spanning Tree (MSST) problem, with applications in secure communication systems, seeks a spanning tree T minimizing maxeTw(e)+eTc(e) on a given edge-weighted undirected network [...] Read more.
The Max+Sum Spanning Tree (MSST) problem, with applications in secure communication systems, seeks a spanning tree T minimizing maxeTw(e)+eTc(e) on a given edge-weighted undirected network G(V,E,c,w), where the sets V and E are the sets of vertices and edges, respectively. The functions c and w are defined on the edge set, representing transmission cost and verification delay in secure communication systems, respectively. This problem can be solved within O(|E|log|V|) time. We investigate its interdiction (MSSTID) and improvement (MSSTIP) problems under the weighted l norm. MSSTID seeks minimal edge weight adjustments (to either c or w) to degrade network performance by ensuring the optimal MSST’s weight is at least K, while MSSTIP similarly aims to enhance performance by making the optimal MSST’s weight at most K through minimal weight modifications. These problems naturally arise in adversarial and proactive performance enhancement scenarios, respectively, where network robustness or efficiency must be guaranteed through constrained resource allocation. We first establish their mathematical models. Subsequently, we analyze the properties of the optimal value to determine the relationship between the magnitude of a given number and the optimal value. Then, utilizing binary search methods and greedy techniques, we design four algorithms with time complexity O(|E|2log|V|) to solve the above problems by modifying w or c. Finally, numerical experiments are conducted to demonstrate the effectiveness of the algorithms. Full article
(This article belongs to the Special Issue Graph Theory and Combinatorics: Theory and Applications)
37 pages, 5079 KB  
Article
The Complexity of Classes of Pyramid Graphs Based on the Fritsch Graph and Its Related Graphs
by Ahmad Asiri and Salama Nagy Daoud
Axioms 2025, 14(8), 622; https://doi.org/10.3390/axioms14080622 - 8 Aug 2025
Viewed by 281
Abstract
A quantitative study of the complicated three-dimensional structures of artificial atoms in the field of intense matter physics requires a collaborative method that combines a statistical analysis of unusual graph features related to atom topology. Simplified circuits can also be produced by using [...] Read more.
A quantitative study of the complicated three-dimensional structures of artificial atoms in the field of intense matter physics requires a collaborative method that combines a statistical analysis of unusual graph features related to atom topology. Simplified circuits can also be produced by using similar transformations to streamline complex circuits that need laborious mathematical calculations during analysis. These modifications can also be used to determine the number of spanning trees required for specific graph families. The explicit derivation of formulas to determine the number of spanning trees for novel pyramid graph types based on the Fritsch graph, which is one of only six graphs in which every neighborhood is a 4- or 5-vertex cycle, is the focus of our study. We conduct this by utilizing our understanding of difference equations, weighted generating function rules, and the strength of analogous transformations found in electrical circuits. Full article
(This article belongs to the Special Issue Graph Theory and Combinatorics: Theory and Applications)
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14 pages, 320 KB  
Article
Odd Cycles in Conditionally Faulty Enhanced Hypercube Networks
by Min Liu
Axioms 2025, 14(3), 201; https://doi.org/10.3390/axioms14030201 - 10 Mar 2025
Viewed by 547
Abstract
The n-dimensional enhanced hypercube Qn,k(1kn1) is a well-known variation of hypercube networks. Its structure can be obtained from the hypercube by adding 2n1 complementary edges. We denote [...] Read more.
The n-dimensional enhanced hypercube Qn,k(1kn1) is a well-known variation of hypercube networks. Its structure can be obtained from the hypercube by adding 2n1 complementary edges. We denote a network G to be a conditionally faulty model if every fault-free vertex of G connects at least two fault-free edges. Let Fv and Fe be the set of faulty vertices and faulty edges in Qn,k(1kn1), respectively. In this paper, for the conditionally faulty Qn,k with |Fv|+|Fe|2n5, where n(3) and k have different parity, I prove that Qn,kFvFe contains a fault-free cycle with every odd length l, where nk+4l2n2|Fv|1. Full article
(This article belongs to the Special Issue Graph Theory and Combinatorics: Theory and Applications)
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16 pages, 372 KB  
Article
An O(kn)-Time Algorithm to Solve Steiner (k, k′)-Eccentricity on Trees
by Xingfu Li
Axioms 2025, 14(3), 166; https://doi.org/10.3390/axioms14030166 - 24 Feb 2025
Viewed by 378
Abstract
Steiner (k,k)-eccentricity on a given fixed k-subset in a graph G is the maximum Steiner distance over all k-subsets of V(G) which contain the fixed k-set, where the Steiner [...] Read more.
Steiner (k,k)-eccentricity on a given fixed k-subset in a graph G is the maximum Steiner distance over all k-subsets of V(G) which contain the fixed k-set, where the Steiner distance of a set is the size of a minimum Steiner tree on this set in a graph. Let RV(T) be the given fixed k-subset in a tree T. Let k1 and k2 be two integers such that k1k2k. We prove that, in a tree, every optimal solution of Steiner (k1,k)-eccentricity on R takes some optimal solution of Steiner (k2,k)-eccentricity on R as a partial solution. On the other hand, every optimal solution of Steiner (k2,k)-eccentricity on R is part of some optimal solution of Steiner (k1,k)-eccentricity on the set R in a tree. Finally, we present an O(kn)-time algorithm to solve Steiner (k,k)-eccentricity on a given fixed k-set in trees. Full article
(This article belongs to the Special Issue Graph Theory and Combinatorics: Theory and Applications)
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33 pages, 3247 KB  
Article
Optimization of General Power-Sum Connectivity Index in Uni-Cyclic Graphs, Bi-Cyclic Graphs and Trees by Means of Operations
by Muhammad Yasin Khan, Gohar Ali and Ioan-Lucian Popa
Axioms 2024, 13(12), 840; https://doi.org/10.3390/axioms13120840 - 28 Nov 2024
Cited by 1 | Viewed by 903
Abstract
The field of indices has been explored and advanced by various researchers for different purposes. One purpose is the optimization of indices in various problems. In this work, the general power-sum connectivity index is considered. The general power-sum connectivity index was investigated for [...] Read more.
The field of indices has been explored and advanced by various researchers for different purposes. One purpose is the optimization of indices in various problems. In this work, the general power-sum connectivity index is considered. The general power-sum connectivity index was investigated for k-generalized quasi-trees where optimal graphs were found. Further, in this work, we extend the idea of optimization to families of graphs, including uni-cyclic graphs, bi-cyclic graphs and trees. The optimization is carried out by means of operations named as Operation A, B, C and D. The first two operations increase the value of the general power-sum connectivity index, while the last two work opposite to Operations A and B. These operations are explained by means of diagrams, where one can easily obtain their working procedures. Full article
(This article belongs to the Special Issue Graph Theory and Combinatorics: Theory and Applications)
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