# Sharp Bounds for the Oriented Diameters of Interval Graphs and 2-Connected Proper Interval Graphs

• Jing Huang
• Dong Ye
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4489)

## Abstract

The diameter diam(H) of a (directed) graph H is the maximum value computed over the lengths of all shortest (directed) paths in H. Given a bridgeless connected graph G, the oriented diameter OD(G) is given by $$OD(G) = \mbox{min}\{diam(H):\ H\ \mbox{is\ an\ orientation\ of}\ G\}$$. In this paper, we show that $$OD(G) \leq \lceil \frac{3}{2} diam(G) \rceil + 1$$ for every connected bridgeless interval graph G. Further, for every 2-connected proper interval graph G, we show $$OD(G) \leq \lceil \frac{5}{4} diam(G) \rceil + 1$$ if diam(G) ≤ 3 and $$OD(G) \leq \lceil \frac{5}{4} diam(G) \rceil$$, otherwise. All the bounds are sharp and improve earlier estimations obtained by Fomin et al.

### Keywords

Diameter orientation oriented diameter interval graph proper interval graph

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