Finding shortest non-trivial cycles in directed graphs on surfaces

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Finding shortest non-trivial cycles in directed graphs on surfaces
Let D be a weighted directed graph cellularly embedded in a surface of genus g, orientable or not, possibly with boundary. We describe algorithms to compute a shortest non-contractible and a shortest surface non-separating cycle in D. This generalizes previous results that only dealt with undirected graphs. Our first algorithm computes such cycles in O(n2 log n) time, where n is the total number of vertices and edges of D, thus matching the complexity of the best known algorithm in the undirected case. It revisits and extends Thomassen’s 3-path condition; the technique applies to other families of cycles as well. We also give an algorithm with subquadratic complexity in the complexity of the input graph, if g is fixed. Specifically, we can solve the problem in O( √ g n3/2 log n) time, using a divide-and-conquer technique that simplifies the graph while preserving the topological properties of its cycles. A variant runs in O(ng log g + n log2 n) for graphs of bounded treewidth....
Sergio Cabello, Éric Colin de Verdiè
Added 10 Jul 2010
Updated 10 Jul 2010
Type Conference
Year 2010
Authors Sergio Cabello, Éric Colin de Verdière, Francis Lazarus
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