A graph is an interval graph if it captures the intersection relation for some set of intervals
on the real line. Formally,
is an interval graph provided that one can assign to each
an interval
such that
is nonempty precisely when
. An interval graph on a list
can be generated using IntervalGraph[l]
in the Wolfram Language package Combinatorica`
.
Star graphs are interval graphs, but cycle graphs (for )
are not (Skiena 1990, p. 164). Determining if a graph is an interval graph and
realizing it can be done in
time (Booth and Lueker 1976; Skiena 1990, p. 164).
A graph
is an interval graph iff the vertices of
can be ordered
, ...,
such that
adj
implies
adj
whenever
(West 2000, p. 346).
Every induced subgraph of an interval graph is itself an interval graph (Jacobson et al. 1991; West 2000, p. 226).