@InProceedings{NodeSteiner_ICALP2009,
AUTHOR = {Erik D. Demaine and MohammadTaghi Hajiaghayi and Philip Klein},
TITLE = {Node-Weighted Steiner Tree and Group Steiner Tree in Planar Graphs},
BOOKTITLE = {Proceedings of the 36th International Colloquium on
Automata, Languages and Programming (ICALP 2009)},
bookurl = {http://icalp09.cti.gr/},
SERIES = {Lecture Notes in Computer Science},
seriesurl = {http://www.springer.de/comp/lncs/},
VOLUME = 5555,
ADDRESS = {Rhodes, Greece},
MONTH = {July 5--12},
YEAR = 2009,
PAGES = {328--340},
doi = {https://dx.doi.org/10.1007/978-3-642-02927-1_28},
dblp = {https://dblp.org/rec/conf/icalp/DemaineHK09a},
comments = {This paper is also available from <A HREF="http://dx.doi.org/10.1007/978-3-642-02927-1_28">SpringerLink</A>.},
copyright = {Copyright held by the authors.},
length = {12 pages},
papers = {NodeSteiner_TAlg},
}
The second problem we address is group Steiner tree: given a graph with edge weights and a collection of groups (subsets of nodes), find a minimum-weight connected subgraph that includes at least one node from each group. The best approximation ratio known in general graphs is O(log3 n), or O(log2 n) when the host graph is a tree. We obtain an O(log n polyloglog n) approximation algorithm for the special case where the graph is planar embedded and each group is the set of nodes on a face. We obtain the same approximation ratio for the minimum-weight tour that must visit each group.