/usr/lib/python2.7/dist-packages/networkx/algorithms/traversal/breadth_first_search.py is in python-networkx 1.8.1-0ubuntu3.
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====================
Breadth-first search
====================
Basic algorithms for breadth-first searching.
"""
__author__ = """\n""".join(['Aric Hagberg <hagberg@lanl.gov>'])
__all__ = ['bfs_edges', 'bfs_tree',
'bfs_predecessors', 'bfs_successors']
import networkx as nx
from collections import defaultdict, deque
def bfs_edges(G, source, reverse=False):
"""Produce edges in a breadth-first-search starting at source."""
# Based on http://www.ics.uci.edu/~eppstein/PADS/BFS.py
# by D. Eppstein, July 2004.
if reverse and isinstance(G, nx.DiGraph):
neighbors = G.predecessors_iter
else:
neighbors = G.neighbors_iter
visited=set([source])
queue = deque([(source, neighbors(source))])
while queue:
parent, children = queue[0]
try:
child = next(children)
if child not in visited:
yield parent, child
visited.add(child)
queue.append((child, neighbors(child)))
except StopIteration:
queue.popleft()
def bfs_tree(G, source, reverse=False):
"""Return directed tree of breadth-first-search from source."""
T = nx.DiGraph()
T.add_node(source)
T.add_edges_from(bfs_edges(G,source,reverse=reverse))
return T
def bfs_predecessors(G, source):
"""Return dictionary of predecessors in breadth-first-search from source."""
return dict((t,s) for s,t in bfs_edges(G,source))
def bfs_successors(G, source):
"""Return dictionary of successors in breadth-first-search from source."""
d=defaultdict(list)
for s,t in bfs_edges(G,source):
d[s].append(t)
return dict(d)
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