,
Shaohua Li,
Wojciech Nadara,
Marcin Smulewicz,
Magnus Wahlström
Creative Commons Attribution 3.0 Unported license
We study the Many Visits TSP problem, where given a number k(v) for each of n cities and pairwise (possibly asymmetric) integer distances, one has to find an optimal tour that visits each city v exactly k(v) times. The currently fastest algorithm is due to Berger, Kozma, Mnich and Vincze [SODA 2019, TALG 2020] and runs in time and space O*(5ⁿ). They also show a polynomial space algorithm running in time O(16^{n+o(n)}). In this work, we show three main results:
- A randomized polynomial space algorithm in time O*(2^n D), where D is the maximum distance between two cities. By using standard methods, this results in a (1+ε)-approximation in time O*(2ⁿε^{-1}). Improving the constant 2 in these results would be a major breakthrough, as it would result in improving the O*(2ⁿ)-time algorithm for Directed Hamiltonian Cycle, which is a 50 years old open problem.
- A tight analysis of Berger et al.’s exponential space algorithm, resulting in an O*(4ⁿ) running time bound.
- A new polynomial space algorithm, running in time O(7.88ⁿ).
@InProceedings{kowalik_et_al:LIPIcs.ESA.2020.66,
author = {Kowalik, {\L}ukasz and Li, Shaohua and Nadara, Wojciech and Smulewicz, Marcin and Wahlstr\"{o}m, Magnus},
title = {{Many Visits TSP Revisited}},
booktitle = {28th Annual European Symposium on Algorithms (ESA 2020)},
pages = {66:1--66:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-162-7},
ISSN = {1868-8969},
year = {2020},
volume = {173},
editor = {Grandoni, Fabrizio and Herman, Grzegorz and Sanders, Peter},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2020.66},
URN = {urn:nbn:de:0030-drops-129329},
doi = {10.4230/LIPIcs.ESA.2020.66},
annote = {Keywords: many visits traveling salesman problem, exponential algorithm}
}