Improved approximation algorithms for metric maximum ATSP and maximum 3-cycle cover problems

We consider an APX-hard variant (Δ-Max-ATSP) and an APX-hard relaxation (Max-3-DCC) of the classical traveling salesman problem. We present a frac(31, 40)-approximation algorithm for Δ-Max-ATSP and a frac(3, 4)-approximation algorithm for Max-3-DCC with polynomial running time. The results are obtained via a new way of applying techniques for computing undirected cycle covers to directed problems. © 2009 Elsevier B.V. All rights reserved.