Autour de la connexité dans les graphes avec conflits

We will look at graphs with conflicts (conflict is a pair of edges can not simultaneously be part of the same subgraph), in which we will study different types of problems related to the existence of subgraphs without conflict. The nature of the problems is both combinatorial and algorithmic. Our guideline is the notion of connectivity. We will see several results, simple without conflict, are no longer when adding conflicts. We will present exact algorithms (not polynomial), \mathcal{N P}-completeness results and sufficient conditions ensuring the existence of certain objects (spanning tree, path and Hamiltonian cycle) without conflict.Nous nous intéresserons aux graphes avec conflits (un conflit est une paire d’arêtes ne pouvant pas simultanément faire partie d’un même sous-graphe), dans lesquels nous étudierons différents types de problèmes liés à l’existence de sous-graphes sans conflit, de nature aussi bien algorithmique que combinatoire, notre ligne directrice étant la notion de connectivité. Nous verrons que plusieurs résultats, simples sans conflit, ne le sont plus lors de l’ajout de conflits. Nous présenterons : des algorithmes exacts (non polynomiaux), des résultats de \mathcal{N P}-complétude, et des conditions suffisantes assurant l’existence de certains objets (arbre couvrant, chemin et cycle hamiltonien) sans conflits

Finding Hamiltonian circuits in quasi-adjoint graphs

This paper is motivated by a method used for DNA sequencing by hybridization presented in [Jacek Blazewicz, Marta Kasprzak, Computational complexity of isothernnic DNA sequencing by hybridization, Discrete Appl. Math. 154 (5) (2006) 718-7291. This paper presents a class of digraphs: the quasi-adjoint graphs. This class includes the ones used in the paper cited above. A polynomial recognition algorithm in O(n(3)), as well as a polynomial algorithm in O(n(2) + m(2)) for finding a Hamiltonian circuit in these graphs are given. Furthermore, some results about related problems such as finding a Eulerian circuit while respecting some forbidden transitions (a path with three vertices) are discussed. (c) 2008 Elsevier B.V. All rights reserved