An Efficient Algorithm to Compute the Toughness in Graphs with Bounded Treewidth

Let t be a positive real number. A graph is called t-tough if the removal of any vertex set S that disconnects the graph leaves at most |S|/t components. The toughness of a graph is the largest t for which the graph is t-tough. We prove that toughness is fixed-parameter tractable parameterized with the treewidth. More precisely, we give an algorithm to compute the toughness of a graph G with running time O(|V(G)|3·tw(G)2tw(G)) where tw(G) is the treewidth. If the treewidth is bounded by a constant, then this is a polynomial algorithm. © The Author(s) 2024.