DistanceSet( gamma, distances, V )
DistanceSet( gamma, distances, V, G )
This function returns the set of vertices w of gamma, such that d(<V>,w) is in distances (a list or singleton distance).
The optional parameter G, if present, is assumed to be a subgroup of Aut(<gamma>) fixing V setwise. Including such a G can speed up the function.
gap> DistanceSet( JohnsonGraph(4,2), 1, [1,6] ); [ 2, 3, 4, 5 ]
GAP 3.4.4