def two_neighborhood(G, v):
"""Returns the set of nodes at distance at most two from `v`.
`G` must be a graph and `v` a node in that graph.
The returned set includes the nodes at distance zero (that is,
the node `v` itself), the nodes at distance one (that is, the
out-neighbors of `v`), and the nodes at distance two.
"""
# TODO This is trivially parallelizable.
return {x for x in G if x == v or x in G[v] or any(is_path(G, [v, z, x]) for z in G)}
def two_neighborhood(G, v):
"""Returns the set of nodes at distance at most two from `v`.
`G` must be a graph and `v` a node in that graph.
The returned set includes the nodes at distance zero (that is,
the node `v` itself), the nodes at distance one (that is, the
out-neighbors of `v`), and the nodes at distance two.
"""
# TODO This is trivially parallelizable.
return {x for x in G
if x == v or x in G[v] or
any(is_path(G, [v, z, x]) for z in G)}