The extremal values of connective eccentricity index for trees and unicyclic graphs

Abstract

Let G be a simple connected graph with vertex set V(G). The connective eccentricity index (CEI) of a graph is defined as ξce(G)=∑v∗∗∗V(G)(d(v)/ε(v)), where ε(v), d(v) denote the eccentricity and the degree of v, respectively. In this paper, we further study the CEI of trees and unicyclic graphs with several graph constraints, we also determine the extremal graphs.