图的Wiener极化指数定义为图中距离为3的无序点对的数目.本文给出仙人掌图的Wiener极化指数的显示表示,并导出若干特殊仙人掌图的极化指数公式.
The Wiener polarity index of a graph G is the number of unordered pairs of vertices u,v such that the distance between u and v is 3. In this paper we give an explicit formula for the Wiener polarity index of cactus graphs. We also deduce formulas for some special cactus graphs.