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Proper orientation of cacti

Julio Araujo 1 Frédéric Havet 2 Claudia Linhares Sales 1 Ana Silva 1 
2 COATI - Combinatorics, Optimization and Algorithms for Telecommunications
CRISAM - Inria Sophia Antipolis - Méditerranée , Laboratoire I3S - COMRED - COMmunications, Réseaux, systèmes Embarqués et Distribués
Abstract : An orientation of a graph G is proper if two adjacent vertices have different in-degrees. The proper-orientation number − → χ (G) of a graph G is the minimum maximum in-degree of a proper orientation of G. In [1], the authors ask whether the proper orientation number of a planar graph is bounded. We prove that every cactus admits a proper orientation with maximum in-degree at most 7. We also prove that the bound 7 is tight by showing a cactus having no proper orientation with maximum in-degree less than 7. We also prove that any planar claw-free graph has a proper orientation with maximum in-degree at most 6 and that this bound can also be attained.
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Submitted on : Wednesday, June 29, 2016 - 12:49:26 AM
Last modification on : Thursday, August 4, 2022 - 4:58:24 PM
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Julio Araujo, Frédéric Havet, Claudia Linhares Sales, Ana Silva. Proper orientation of cacti. Theoretical Computer Science, 2016, 639, pp.14-25. ⟨10.1016/j.tcs.2016.05.016⟩. ⟨hal-01338646⟩



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