# Eccentricity function in distance-hereditary graphs

## TL;DR

This paper investigates the eccentricity function in distance-hereditary graphs, proving its near-unimodality, characterizing graph centers, and introducing an efficient linear-time algorithm for eccentricity computation.

## Contribution

It establishes the near-unimodality of eccentricity in distance-hereditary graphs, characterizes their centers, and presents a new linear-time algorithm for computing all eccentricities.

## Key findings

- Eccentricity function is almost unimodal in distance-hereditary graphs.
- Complete characterization of centers in these graphs.
- Development of a linear-time algorithm for eccentricity computation.

## Abstract

A graph $G=(V,E)$ is distance hereditary if every induced path of $G$ is a shortest path. In this paper, we show that the eccentricity function $e(v)=\max\{d(v,u): u\in V\}$ in any distance-hereditary graph $G$ is almost unimodal, that is, every vertex $v$ with $e(v)> rad(G)+1$ has a neighbor with smaller eccentricity. Here, $rad(G)=\min\{e(v): v\in V\}$ is the radius of graph $G$. Moreover, we use this result to fully characterize the centers of distance-hereditary graphs. Several bounds on the eccentricity of a vertex with respect to its distance to the center of $G$ or to the ends of a diametral path are established. Finally, we propose a new linear time algorithm to compute all eccentricities in a distance-hereditary graph.