Circular convex bipartite graphs: Feedback vertex sets

A feedback vertex set   is a subset of vertices, such that the removal of this subset renders the remaining graph cycle-free. The weight of a feedback vertex set is the sum of weights of its vertices. Finding a minimum weighted feedback vertex set is tractable for convex bipartite graphs, but NPNP-complete even for unweighted bipartite graphs. In a circular convex (convex, respectively) bipartite graph, there is a circular (linear, respectively) ordering defined on one class of vertices, such that for every vertex in another class, the neighborhood of this vertex is a circular arc (an interval, respectively). The minimum weighted feedback vertex set problem is shown tractable for circular convex bipartite graphs in this paper, by making a Cook reduction (i.e. polynomial time Turing reduction) for this problem from circular convex bipartite graphs to convex bipartite graphs.