Let D be a strongly connected directed graph of order n≥4. In Bang-Jensen et al. (1996), (J. of Graph Theory 22 (2) (1996) 181–187), J. Bang-Jensen, G. Gutin and H. Li proved the following theorems: If (∗)d(x)+d(y)≥2n−1 and min{d(x),d(y)}≥n−1 for every pair of non-adjacent vertices x,y with a common in-neighbour or (∗∗)min{d+(x)+d−(y),d−(x)+d+(y)}≥n for every pair of non-adjacent vertices x,y with a common in-neighbour or a common out-neighbour, then D is Hamiltonian. In this paper we show that: (i) if D satisfies condition (∗) and the minimum semi-degree of D at least two or (ii) if D is not directed cycle and satisfies condition (∗∗), then either D contains a cycle of length n−1 or n is even and D is isomorphic to the complete bipartite digraph or to the complete bipartite digraph minus one arc.
oai:noad.sci.am:136097
samdarbin@ipia.sci.am ; isko@ipia.sci.am
Institute for Informatics and Automation Problems
Apr 19, 2021
Apr 19, 2021
15
https://noad.sci.am/publication/149560
Հրատարակության անուն | Ամսաթիվ |
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Samvel Kh Darbinyan, On longest non-Hamiltonian cycles in digraphs with the conditions of Bang-Jensen, Gutin and Li | Apr 19, 2021 |
Դարբինյան Սամվել Կարապետյան Իսկանդար
Darbinyan Samvel Karapetyan Iskandar
Darbinyan Samvel