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We investigate a new oriented variant of the Firefighter Problem. In the traditional Firefighter Problem, a fire breaks out at a given vertex of a graph, and at each time interval spreads to neighbouring vertices that have not been protected, while a constant number of vertices are protected at each time interval. In the version of the problem considered here, the firefighters are able to orient the edges of the graph before the fire breaks out, but the fire could start at any vertex. We consider this problem when played on a graph in one of several graph classes, and give upper and lower bounds on the number of vertices that can be saved. In particular, when one firefighter is available at each time interval, and the given graph is a complete graph, or a complete bipartite graph, we present firefighting strategies that are provably optimal. We also provide lower bounds on the number of vertices that can be saved as a function of the chromatic number, of the maximum degree, and of the treewidth of a graph. For a subcubic graph, we show that the firefighters can save all but two vertices, and this is best possible.
Let $G$ be a graph(directed or undirected) having $k$ number of blocks. A $mathcal{B}$-partition of $G$ is a partition into $k$ vertex-disjoint subgraph $(hat{B_1},hat{B_1},hdots,hat{B_k})$ such that $hat{B}_i$ is induced subgraph of $B_i$ for $i=1,2
We consider the NP-complete problem of tracking paths in a graph, first introduced by Banik et. al. [3]. Given an undirected graph with a source $s$ and a destination $t$, find the smallest subset of vertices whose intersection with any $s-t$ path re
We initiate the study of computational complexity of graph coverings, aka locally bijective graph homomorphisms, for {em graphs with semi-edges}. The notion of graph covering is a discretization of coverings between surfaces or topological spaces, a
We revisit a concept that has been central in some early stages of computer science, that of structured programming: a set of rules that an algorithm must follow in order to acquire a structure that is desirable in many aspects. While much has been w
For any class $mathcal{C}$ of bipartite graphs, we define quasi-$cal C$ to be the class of all graphs $G$ such that every bipartition of $G$ belongs to $cal C$. This definition is motivated by a generalisation of the switch Markov chain on perfect ma