关键词: 围长, 单圈图, Harary指数, 反距离

Abstract: In this paper,we first give a formula for calculating the Harary index of a unicyclic graph according to the structure,and then using this formula,we obtain the maximum value for the Harary index of unicyclic graphs with a given girth,and characterize the extremal graph with respect to the Harary index.

Key words: Girth, Unicyclic graph, Harary index, Reciprocal distance