A 5-approximation algorithm for the k-prize-collecting Steiner tree problem

In this paper, we consider the k-prize-collecting Steiner tree problem (k-PCST), extending both the prize-collecting Steiner tree problem (PCST) and the k-minimum spanning tree problem (k-MST). In this problem, we are given a connected graph $$G = (V, E)$$G=(V,E), a root vertex r and an integer k. Every edge in E has a nonnegative cost. Every vertex in V has a nonnegative penalty cost. We want to find an r-rooted tree F that spans at least k vertices such that the total cost, including the edge cost of the tree F and the penalty cost of the vertices not spanned by F, is minimized. Our main contribution is to present a 5-approximation algorithm for the k-PCST via the methods of primal–dual and Lagrangean relaxation.

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