Guo(Discrete Appl.Math.95(1999)273-277)提出外路的概念.有向图中一个顶点x(或弧xy)的一条外路是指起始于x(或弧xy)的一条路使得x控制这条路的终点仅当终点也控制x.一条长为k的外路称为k-外路.本文证明了一个几乎正则c-部(c≥8)竞赛图D中,如果D的每个部集至少包含两个点,则D中每条弧有(k-1)-或k-外路,其中k∈{3,4,…,|V(D)|-1}.进一步,当D是一个几乎正则c-部(c≥8)竞赛图,且每个部集所含顶点数目相同时,D的每条弧在k-或(k+1)-圈中,其中k∈{3,4,…,|V(D)|-1}.
Guo (Discrete Appl. Math. 95 (1999) 273-277) proposed the concept of out-path. An outpath of a vertex x (an arc xy, respectively) in a digraph is a path starting at x (an arc xy, respectively) such that x dominates the endvertex of the path only if the endvertex also dominates x. A k-outpath is an outpath of length k. In this article, the following results are proved: Let D be an almost regular c-partite tournament. If each partite set contains at least two vertices, then every arc of D has a (k - 1)- or k-outpath for each k ∈ {3, 4,…, |V(D)|- 1}. Furthermore, if D is an almost regular c-partite (c 〉 8) tournament with the partite sets V1, V2,…, Vc such that |V 1| = |V2| |Vc|, then every arc of D is contained in a k- or (k + 1)-cycle for each k ∈ {3,4,..., |V(D)| - 1}.