def spanning_tree(tree, preserve):
""" Return a new DiGraph with the spanning tree including the desired nodes.
preserve: the set of nodes that delimit the spanning tree. """
spanning = DiGraph()
preserve = set(preserve) # duplicate, will be altered
if 1 == len(preserve):
spanning.add_node(iter(preserve).next())
return spanning
if len(tree.successors(find_root(tree))) > 1:
tree = tree.copy()
# First end node found
endNode = (node for node in tree
if not next(tree.successors_iter(node), None)).next()
reroot(tree, endNode)
n_seen = 0
# Start from shortest sequence
for seq in sorted(partition(tree), key=len):
path = []
for node in seq:
if node in preserve:
path.append(node)
if node not in spanning:
n_seen += 1
if len(preserve) == n_seen:
break
elif path:
path.append(node)
if path:
spanning.add_path(path)
if seq[-1] == path[-1]:
preserve.add(path[-1])
if len(preserve) == n_seen:
break
return spanning
def spanning_tree(tree, preserve):
""" Return a new DiGraph with the spanning tree including the desired nodes.
preserve: the set of nodes that delimit the spanning tree. """
spanning = DiGraph()
preserve = set(preserve) # duplicate, will be altered
if 1 == len(preserve):
spanning.add_node(iter(preserve).next())
return spanning
if len(tree.successors(find_root(tree))) > 1:
tree = tree.copy()
# First end node found
endNode = (node for node in tree if not next(tree.successors_iter(node), None)).next()
reroot(tree, endNode)
n_seen = 0
# Start from shortest sequence
for seq in sorted(partition(tree), key=len):
path = []
for node in seq:
if node in preserve:
path.append(node)
if node not in spanning:
n_seen += 1
if len(preserve) == n_seen:
break
elif path:
path.append(node)
if path:
spanning.add_path(path)
if seq[-1] == path[-1]:
preserve.add(path[-1])
if len(preserve) == n_seen:
break
return spanning
