一个双色有向图D是本原的,如果存在非负整数h和k,h+k〉0,使得D的每对顶点(i,j),都存在从i到j的(h,k)-一途径。此时,把h+k的最小值定义为双色有向图D的本原指数,文章给出一类特殊双色有向图的本原指数集,并对极图进行了刻化。
A two-colored digraph D is primitive. If there exist nonnegative integers h and k with h + k 〉 0 such that for each pair (i,j) of vertices there exists an (h ,k) -path in D from i to j. The exponent of the primitive two- colored digraph D is the minimum value of h + k taken over all such h and k. In this paper, we give the exponent set of a class of primitive two-colored digraphs, and the characterizations of the extreme two-colored digraphs.