极小强连通有向图顶点指数为4的顶点性质

摘要

通过证明得到了极小强连通有向图顶点指数为4的顶点性质：（1）过顶点指数为4的顶点必有长为3的圈；（2）顶点指数为4的顶点的出度不小于2；（3）长为3的圈上至少有一个顶点的指数不为4。%Let D= （V,E） is minimally strongly connected digraph, In this paper, we obtain some properties of vertex with point exponent 4 of D that if expo（u） = 4 ,then there is a circle of length 3 passing through vertex u, and out degree ofu is at least 2. In addition, on any circle of length 3 in D, there is at least a vertex which point exponent is not 4.