Traveling salesman games with the Monge property

  • Authors:
  • Yoshio Okamoto

  • Affiliations:
  • Institute of Theoretical Computer Science, Department of Computer Science, ETH Zürich, CH-8092, Zürich, Switzerland

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2004

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Abstract

Several works have indicated the relationships between polynomially solvable combinatorial optimization problems and the core non-emptiness of cooperative games associated with them, and between intractable combinatorial optimization problems and the hardness of the problem to decide the core non-emptiness of the associated games. In this paper, we study the core of a traveling salesman game, which is associated with the traveling salesman problem. First, we show that in general the problem to test the core non-emptiness of a given traveling salesman game is NP-hard. This corresponds to the NP-hardness of the traveling salesman problem. Second, we show that the core of a traveling salesman game is non-empty if the distance matrix is a symmetric Monge matrix, and also that a traveling salesman game is submodular (or concave) if the distance matrix is a Kalmanson matrix. These correspond to the fact that the Monge property and the Kalmanson property are polynomially solvable special cases of the traveling salesman problem.