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Checking the admissibility of odd-vertex pairings is hard. (English) Zbl 07533120

Summary: Nash-Williams proved that every graph has a well-balanced orientation. A key ingredient in his proof is admissible odd-vertex pairings. We show that for two slightly different definitions of admissible odd-vertex pairings, deciding whether a given odd-vertex pairing is admissible is co-NP-complete. This resolves a question of Frank. We also show that deciding whether a given graph has an orientation that satisfies arbitrary local arc-connectivity requirements is NP-complete.

MSC:

68R10 Graph theory (including graph drawing) in computer science
05C20 Directed graphs (digraphs), tournaments
05C40 Connectivity
68Q17 Computational difficulty of problems (lower bounds, completeness, difficulty of approximation, etc.)

References:

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[2] Ford, L. R.; Fulkerson, D. R., Flows in Networks (1962), Princeton Univ. Press: Princeton Univ. Press PrincetonNJ · Zbl 0106.34802
[3] Frank, A., Connections in Combinatorial Optimization (2011), Oxford University Press · Zbl 1228.90001
[4] Garey, M.; Johnson, D., Computers and Intractability: a Guide to the Theory Of NP-Completeness (1979), W.H. Freeman · Zbl 0411.68039
[5] Király, Z.; Szigeti, Z., Simultaneous well-balanced orientations of graphs, J. Combin. Theory Ser. B, 96, 5, 684-692 (2006) · Zbl 1098.05048
[6] Menger, K., Zur allgemeinen Kurventheorie, Fund. Math., 10, 96-155 (1927) · JFM 53.0561.01
[7] Nash-Williams, C. St. J.A., On orientations, connectivity, and odd-vertex pairings in finite graphs, Canad. J. Math., 12, 555-567 (1960) · Zbl 0096.38002
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