Directed circuits on a torus


Given verticess, t of a planar digraphG, does there exist a directed circuit ofG containing boths andt? We give a polynomial algorithm for this and for a number of related problems, including one about disjoint directed circuits of prescribed homotopy in a digraph drawn on a torus.

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Seymour, P.D. Directed circuits on a torus. Combinatorica 11, 261–273 (1991).

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AMS subject classification (1980)

  • 05 C 70
  • 05 C 10
  • 05 C 20
  • 05 C 38