Abstract
The paper presents an \(O^*(1.2312^n)\)-time and polynomial-space algorithm for the traveling salesman problem in an \(n\)-vertex graph with maximum degree 3. This improves all previous time bounds of polynomial-space algorithms for this problem. Our algorithm is a simple branch-and-search algorithm with only one branch rule designed on a cut-circuit structure of a graph induced by unprocessed edges. To improve a time bound by a simple analysis on measure and conquer, we introduce an amortization scheme over the cut-circuit structure by defining the measure of an instance to be the sum of not only weights of vertices but also weights of connected components of the induced graph.
Similar content being viewed by others
References
Björklund, A.: Determinant sums for undirected Hamiltonicity. In: Proceedings of 51st Annual IEEE Symposium on Foundations of Computer Science, pp. 173–182 (2010)
Björklund, A., Husfeldt, T., Kasaki, P., Koivisto, M.: The travelling salesman problem in bounded degree graphs. In: Aceto, L., et al. (eds.) ICALP 2008, LNCS 5125, pp. 198–209 (2008)
Bodlaender, H.L., Cygan, M., Kratsch, S., Nederlof, J.: Deterministic single exponential time algorithms for connectivity problems parameterized by treewidth. In: Fomin, F.V., et al. (eds.) ICALP 2013, LNCS 7965, pp. 196–207 (2013)
Dorn, F., Penninkx, E., Bodlaender, H.L., Fomin, F.V.: Efficient exact algorithms on planar graphs: exploiting sphere cut decompositions. Algorithmica 58(3), 790–810 (2010)
Eppstein, D.: Quasiconvex analysis of multivariate recurrence equations for backtracking algorithms. ACM Trans. Algorithms 2(4), 492–509 (2006)
Eppstein, D.: The traveling salesman problem for cubic graphs. J. Gr. Algorithms Appl. 11(1), 61–81 (2007)
Fomin, F., Grandoni, F., Grandoni, F., Kratsch, D.: Measure and conquer: domination: a case study. In: Caires, L., et al. (eds.) ICALP 2005, LNCS 3580, pp. 191–203. Springer, Berlin (2005)
Fomin, F.V., Kratsch, D.: Exact Exponential Algorithms. Springer, Berlin (2010)
Gebauer, H.: Finding and enumerating Hamilton cycles in 4-regular graphs. Theor. Comput. Sci. 412(35), 4579–4591 (2011)
Iwama, K., Nakashima, T.: An improved exact algorithm for cubic graph TSP. In: Lin, G. (ed.) COCOON 2007. LNCS 4598, pp. 108–117 (2007)
Liśkiewicz, M., Schuster, M.R.: A new upper bound for the traveling salesman problem in cubic graphs. J. Discrete Algorithms 27, 1–20 (2014)
Nagamochi, H., Ibaraki, T.: A linear time algorithm for computing 3-edge-connected components in multigraphs. J. Jpn. Soc. Ind. Appl. Math. 9(2), 163–180 (1992)
Nagamochi, H., Ibaraki, T.: Algorithmic Aspects of Graph Connectivities, Encyclopedia of Mathematics and its Applications. Cambridge University Press, Cambridge (2008)
Woeginger, G.J.: Exact algorithms for NP-hard problems: a survey. In: Junger, M., Reinelt, G., Rinaldi, G. (eds.) Combinatorial Optimization. LNCS 2570, pp. 185–207 (2003)
Xiao, M., Nagamochi, H.: An improved exact algorithm for TSP in degree-\(4\) graphs. In: Gudmundsson, J., Mestre, J., Viglas, T. (eds.) COCOON 2012. LNCS 7434, pp. 74–85 (2012)
Author information
Authors and Affiliations
Corresponding author
Additional information
Supported by National Natural Science Foundation of China under the Grant 61370071 and Fundamental Research Funds for the Central Universities under the Grant ZYGX2012J069.
Rights and permissions
About this article
Cite this article
Xiao, M., Nagamochi, H. An Exact Algorithm for TSP in Degree-3 Graphs Via Circuit Procedure and Amortization on Connectivity Structure. Algorithmica 74, 713–741 (2016). https://doi.org/10.1007/s00453-015-9970-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00453-015-9970-4