Exact Algorithms for Exact Satisfiability and Number of Perfect Matchings

Springer Science and Business Media LLC - Tập 52 - Trang 226-249 - 2007
Andreas Björklund1, Thore Husfeldt1
1Department of Computer Science, Lund University, Lund, Sweden

Tóm tắt

We present exact algorithms with exponential running times for variants of n-element set cover problems, based on divide-and-conquer and on inclusion–exclusion characterizations. We show that the Exact Satisfiability problem of size l with m clauses can be solved in time 2 m l O(1) and polynomial space. The same bounds hold for counting the number of solutions. As a special case, we can count the number of perfect matchings in an n-vertex graph in time 2 n n O(1) and polynomial space. We also show how to count the number of perfect matchings in time O(1.732 n ) and exponential space. We give a number of examples where the running time can be further improved if the hypergraph corresponding to the set cover instance has low pathwidth. This yields exponential-time algorithms for counting k-dimensional matchings, Exact Uniform Set Cover, Clique Partition, and Minimum Dominating Set in graphs of degree at most three. We extend the analysis to a number of related problems such as TSP and Chromatic Number.

Tài liệu tham khảo

Byskov, J.M.: Exact algorithms for graph colouring and exact satisfiability. Ph.D. thesis, University of Aarhus (2004)

Dahllöf, V., Jonsson, P., Beigel, R.: Algorithms for four variants of exact satisfiability. Theor. Comput. Sci. 320(2–3), 373–394 (2004)

Feige, U., Kilian, J.: Exponential time algorithms for computing the bandwidth of a graph. Manuscript. Cited in [38]

Lovász, L., Plummer, M.D.: Matching Theory. North-Holland, Amsterdam (1986)

Monien, B., Speckenmeyer, E., Vornberger, O.: Upper bounds for covering problems. Methods Oper. Res. 43, 419–431 (1981)

Ryser, H.J.: Combinatorial Mathematics. Carus Math. Monographs, no. 14. Math. Assoc. of America, Washington, DC (1963)