We consider the NP-complete problem of tracking paths in a graph, first introduced by Banik et al. [Banik et al., 2017]. Given an undirected graph with a source s and a destination t, find the smallest subset of vertices whose intersection with any s-t path results in a unique sequence. In this paper, we show that this problem remains NP-complete when the graph is planar and we give a 4-approximation algorithm in this setting. We also show, via Courcelle’s theorem, that it can be solved in linear time for graphs of bounded-clique width, when its clique decomposition is given in advance.
@InProceedings{eppstein_et_al:LIPIcs.ISAAC.2019.54, author = {Eppstein, David and Goodrich, Michael T. and Liu, James A. and Matias, Pedro}, title = {{Tracking Paths in Planar Graphs}}, booktitle = {30th International Symposium on Algorithms and Computation (ISAAC 2019)}, pages = {54:1--54:17}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-130-6}, ISSN = {1868-8969}, year = {2019}, volume = {149}, editor = {Lu, Pinyan and Zhang, Guochuan}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2019.54}, URN = {urn:nbn:de:0030-drops-115500}, doi = {10.4230/LIPIcs.ISAAC.2019.54}, annote = {Keywords: Approximation Algorithm, Courcelle’s Theorem, Clique-Width, Planar, 3-SAT, Graph Algorithms, NP-Hardness} }
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