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The number of vertices whose out-arcs are pancyclic in a 2-strong tournament
Authors:Ruijuan Li  Shengjia Li  Jinfeng Feng
Institution:a School of Mathematical Sciences, Shanxi University, 030006 Taiyuan, PR China
b Lehrstuhl C für Mathematik, RWTH Aachen University, 52056 Aachen, Germany
Abstract:An arc going out from a vertex x in a digraph is called an out-arc of x. Yao et al. Discrete Appl. Math. 99 (2000) 245-249] proved that every strong tournament contains a vertex x such that all out-arcs of x are pancyclic. Recently, Yeo J. Graph Theory 50 (2005) 212-219] proved that each 3-strong tournament contains two such vertices. In this paper, we confirm that Yeo's result is also true for 2-strong tournaments. Our proof implies a polynomial algorithm to find two such vertices.
Keywords:Tournaments  Cycles  Pancyclicity
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