An improved fully polynomial randomized approximation scheme (FPRAS) for counting the number of Hamiltonian cycles in dense digraphs

  • Authors:
  • Jinshan Zhang;Fengshan Bai

  • Affiliations:
  • -;-

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2011

Quantified Score

Hi-index 5.23

Visualization

Abstract

We propose an improved algorithm for counting the number of Hamiltonian cycles in a directed graph. The basic idea of the method is sequential acceptance/rejection, which is successfully used in approximating the number of perfect matchings in dense bipartite graphs. As a consequence, a new ratio of the number of Hamiltonian cycles to the number of 1-factors is proposed. Based on this ratio, we prove that our algorithm runs in expected time of O(n^8^.^5) for dense problems. This improves the Markov chain Monte Carlo method, the most powerful existing method, by a factor of at least n^4^.^5(logn)^4 in running time. This class of dense problems is shown to be nontrivial in counting, in the sense that they are #P-Complete.