Abstract
For an edge-weighted graph \(G=(V,E,w)\), in which the vertices are partitioned into k clusters \(\mathcal {R}=\{R_1,R_2,\ldots ,R_k\}\), a spanning tree T of G is a clustered spanning tree if T can be cut into k subtrees by removing \(k-1\) edges such that each subtree is a spanning tree for one cluster. In this paper, we show the inapproximability of finding a clustered spanning tree with minimum routing cost, where the routing cost is the total distance summed over all pairs of vertices. We present a 2-approximation for the case that the input is a complete weighted graph whose edge weights obey the triangle inequality. We also study a variant in which the objective function is the total distance summed over all pairs of vertices of different clusters. We show that the problem is polynomial-time solvable when the number of clusters k is 2 and NP-hard for \(k=3\). Finally, we propose a polynomial-time 2-approximation algorithm for the case of three clusters.
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Acknowledgments
This work was supported in part by NSC 101-2221-E-194-025-MY3 and MOST 103-2221-E-194-025-MY3 from National Science Council/Ministry of Science and Technology, Taiwan, ROC
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Lin, CW., Wu, B.Y. On the minimum routing cost clustered tree problem. J Comb Optim 33, 1106–1121 (2017). https://doi.org/10.1007/s10878-016-0026-8
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DOI: https://doi.org/10.1007/s10878-016-0026-8