def to_vertex_cover(G, matching):
"""Returns the minimum vertex cover corresponding to the given maximum
matching of the bipartite graph `G`.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
matching : dictionary
A dictionary whose keys are vertices in `G` and whose values are the
distinct neighbors comprising the maximum matching for `G`, as returned
by, for example, :func:`maximum_matching`. The dictionary *must*
represent the maximum matching.
Returns
-------
vertex_cover : :class:`set`
The minimum vertex cover in `G`.
Notes
-----
This function is implemented using the procedure guaranteed by `Konig's
theorem
<http://en.wikipedia.org/wiki/K%C3%B6nig%27s_theorem_%28graph_theory%29>`_,
which proves an equivalence between a maximum matching and a minimum vertex
cover in bipartite graphs.
Since a minimum vertex cover is the complement of a maximum independent set
for any graph, one can compute the maximum independent set of a bipartite
graph this way:
>>> import networkx as nx
>>> G = nx.complete_bipartite_graph(2, 3)
>>> matching = nx.bipartite.maximum_matching(G)
>>> vertex_cover = nx.bipartite.to_vertex_cover(G, matching)
>>> independent_set = set(G) - vertex_cover
>>> print(list(independent_set))
[2, 3, 4]
"""
# This is a Python implementation of the algorithm described at
# <https://en.wikipedia.org/wiki/K%C3%B6nig%27s_theorem_%28graph_theory%29#Proof>.
L, R = bipartite_sets(G)
# Let U be the set of unmatched vertices in the left vertex set.
unmatched_vertices = set(G) - set(matching)
U = unmatched_vertices & L
# Let Z be the set of vertices that are either in U or are connected to U
# by alternating paths.
Z = _connected_by_alternating_paths(G, matching, U)
# At this point, every edge either has a right endpoint in Z or a left
# endpoint not in Z. This gives us the vertex cover.
return (L - Z) | (R & Z)
def to_vertex_cover(G, matching):
"""Returns the minimum vertex cover corresponding to the given maximum
matching of the bipartite graph `G`.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
matching : dictionary
A dictionary whose keys are vertices in `G` and whose values are the
distinct neighbors comprising the maximum matching for `G`, as returned
by, for example, :func:`maximum_matching`. The dictionary *must*
represent the maximum matching.
Returns
-------
vertex_cover : :class:`set`
The minimum vertex cover in `G`.
Notes
-----
This function is implemented using the procedure guaranteed by `Konig's
theorem
<http://en.wikipedia.org/wiki/K%C3%B6nig%27s_theorem_%28graph_theory%29>`_,
which proves an equivalence between a maximum matching and a minimum vertex
cover in bipartite graphs.
Since a minimum vertex cover is the complement of a maximum independent set
for any graph, one can compute the maximum independent set of a bipartite
graph this way:
>>> import networkx as nx
>>> G = nx.complete_bipartite_graph(2, 3)
>>> matching = nx.bipartite.maximum_matching(G)
>>> vertex_cover = nx.bipartite.to_vertex_cover(G, matching)
>>> independent_set = set(G) - vertex_cover
>>> print(list(independent_set))
[2, 3, 4]
"""
# This is a Python implementation of the algorithm described at
# <https://en.wikipedia.org/wiki/K%C3%B6nig%27s_theorem_%28graph_theory%29#Proof>.
L, R = bipartite_sets(G)
# Let U be the set of unmatched vertices in the left vertex set.
unmatched_vertices = set(G) - set(matching)
U = unmatched_vertices & L
# Let Z be the set of vertices that are either in U or are connected to U
# by alternating paths.
Z = _connected_by_alternating_paths(G, matching, U)
# At this point, every edge either has a right endpoint in Z or a left
# endpoint not in Z. This gives us the vertex cover.
return (L - Z) | (R & Z)
def hopcroft_karp_matching(G):
"""Returns the maximum cardinality matching of the bipartite graph `G`.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
Returns
-------
matches : dictionary
The matching is returned as a dictionary, `matches`, such that
``matches[v] == w`` if node ``v`` is matched to node ``w``. Unmatched
nodes do not occur as a key in mate.
Notes
-----
This function is implemented with the `Hopcroft--Karp matching algorithm
<https://en.wikipedia.org/wiki/Hopcroft%E2%80%93Karp_algorithm>`_ for
bipartite graphs.
See Also
--------
eppstein_matching
References
----------
.. [1] John E. Hopcroft and Richard M. Karp. "An n^{5 / 2} Algorithm for
Maximum Matchings in Bipartite Graphs" In: **SIAM Journal of Computing**
2.4 (1973), pp. 225--231. <https://dx.doi.org/10.1137/0202019>.
"""
# First we define some auxiliary search functions.
#
# If you are a human reading these auxiliary search functions, the "global"
# variables `leftmatches`, `rightmatches`, `distances`, etc. are defined
# below the functions, so that they are initialized close to the initial
# invocation of the search functions.
def breadth_first_search():
for v in left:
if leftmatches[v] is None:
distances[v] = 0
queue.append(v)
else:
distances[v] = INFINITY
distances[None] = INFINITY
while queue:
v = queue.popleft()
if distances[v] < distances[None]:
for u in G[v]:
if distances[rightmatches[u]] is INFINITY:
distances[rightmatches[u]] = distances[v] + 1
queue.append(rightmatches[u])
return distances[None] is not INFINITY
def depth_first_search(v):
if v is not None:
for u in G[v]:
if distances[rightmatches[u]] == distances[v] + 1:
if depth_first_search(rightmatches[u]):
rightmatches[u] = v
leftmatches[v] = u
return True
distances[v] = INFINITY
return False
return True
# Initialize the "global" variables that maintain state during the search.
left, right = bipartite_sets(G)
leftmatches = {v: None for v in left}
rightmatches = {v: None for v in right}
distances = {}
queue = collections.deque()
# Implementation note: this counter is incremented as pairs are matched but
# it is currently not used elsewhere in the computation.
num_matched_pairs = 0
while breadth_first_search():
for v in left:
if leftmatches[v] is None:
if depth_first_search(v):
num_matched_pairs += 1
# Strip the entries matched to `None`.
leftmatches = {k: v for k, v in leftmatches.items() if v is not None}
rightmatches = {k: v for k, v in rightmatches.items() if v is not None}
# At this point, the left matches and the right matches are inverses of one
# another. In other words,
#
# leftmatches == {v, k for k, v in rightmatches.items()}
#
# Finally, we combine both the left matches and right matches.
return dict(itertools.chain(leftmatches.items(), rightmatches.items()))
def hopcroft_karp_matching(G, top_nodes=None):
"""Returns the maximum cardinality matching of the bipartite graph `G`.
A matching is a set of edges that do not share any nodes. A maximum
cardinality matching is a matching with the most edges possible. It
is not always unique. Finding a matching in a bipartite graph can be
treated as a networkx flow problem.
The functions ``hopcroft_karp_matching`` and ``maximum_matching``
are aliases of the same function.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
top_nodes : container of nodes
Container with all nodes in one bipartite node set. If not supplied
it will be computed. But if more than one solution exists an exception
will be raised.
Returns
-------
matches : dictionary
The matching is returned as a dictionary, `matches`, such that
``matches[v] == w`` if node `v` is matched to node `w`. Unmatched
nodes do not occur as a key in `matches`.
Raises
------
AmbiguousSolution
Raised if the input bipartite graph is disconnected and no container
with all nodes in one bipartite set is provided. When determining
the nodes in each bipartite set more than one valid solution is
possible if the input graph is disconnected.
Notes
-----
This function is implemented with the `Hopcroft--Karp matching algorithm
<https://en.wikipedia.org/wiki/Hopcroft%E2%80%93Karp_algorithm>`_ for
bipartite graphs.
See :mod:`bipartite documentation <networkx.algorithms.bipartite>`
for further details on how bipartite graphs are handled in NetworkX.
See Also
--------
maximum_matching
hopcroft_karp_matching
eppstein_matching
References
----------
.. [1] John E. Hopcroft and Richard M. Karp. "An n^{5 / 2} Algorithm for
Maximum Matchings in Bipartite Graphs" In: **SIAM Journal of Computing**
2.4 (1973), pp. 225--231. <https://doi.org/10.1137/0202019>.
"""
# First we define some auxiliary search functions.
#
# If you are a human reading these auxiliary search functions, the "global"
# variables `leftmatches`, `rightmatches`, `distances`, etc. are defined
# below the functions, so that they are initialized close to the initial
# invocation of the search functions.
def breadth_first_search():
for v in left:
if leftmatches[v] is None:
distances[v] = 0
queue.append(v)
else:
distances[v] = INFINITY
distances[None] = INFINITY
while queue:
v = queue.popleft()
if distances[v] < distances[None]:
for u in G[v]:
if distances[rightmatches[u]] is INFINITY:
distances[rightmatches[u]] = distances[v] + 1
queue.append(rightmatches[u])
return distances[None] is not INFINITY
def depth_first_search(v):
if v is not None:
for u in G[v]:
if distances[rightmatches[u]] == distances[v] + 1:
if depth_first_search(rightmatches[u]):
rightmatches[u] = v
leftmatches[v] = u
return True
distances[v] = INFINITY
return False
return True
# Initialize the "global" variables that maintain state during the search.
left, right = bipartite_sets(G, top_nodes)
leftmatches = {v: None for v in left}
rightmatches = {v: None for v in right}
distances = {}
queue = collections.deque()
# Implementation note: this counter is incremented as pairs are matched but
# it is currently not used elsewhere in the computation.
num_matched_pairs = 0
while breadth_first_search():
for v in left:
if leftmatches[v] is None:
if depth_first_search(v):
num_matched_pairs += 1
# Strip the entries matched to `None`.
leftmatches = {k: v for k, v in leftmatches.items() if v is not None}
rightmatches = {k: v for k, v in rightmatches.items() if v is not None}
# At this point, the left matches and the right matches are inverses of one
# another. In other words,
#
# leftmatches == {v, k for k, v in rightmatches.items()}
#
# Finally, we combine both the left matches and right matches.
return dict(itertools.chain(leftmatches.items(), rightmatches.items()))
def to_vertex_cover(G, matching, top_nodes=None):
"""Returns the minimum vertex cover corresponding to the given maximum
matching of the bipartite graph `G`.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
matching : dictionary
A dictionary whose keys are vertices in `G` and whose values are the
distinct neighbors comprising the maximum matching for `G`, as returned
by, for example, :func:`maximum_matching`. The dictionary *must*
represent the maximum matching.
top_nodes : container
Container with all nodes in one bipartite node set. If not supplied
it will be computed. But if more than one solution exists an exception
will be raised.
Returns
-------
vertex_cover : :class:`set`
The minimum vertex cover in `G`.
Raises
------
AmbiguousSolution
Raised if the input bipartite graph is disconnected and no container
with all nodes in one bipartite set is provided. When determining
the nodes in each bipartite set more than one valid solution is
possible if the input graph is disconnected.
Notes
-----
This function is implemented using the procedure guaranteed by `Konig's
theorem
<https://en.wikipedia.org/wiki/K%C3%B6nig%27s_theorem_%28graph_theory%29>`_,
which proves an equivalence between a maximum matching and a minimum vertex
cover in bipartite graphs.
Since a minimum vertex cover is the complement of a maximum independent set
for any graph, one can compute the maximum independent set of a bipartite
graph this way:
>>> G = nx.complete_bipartite_graph(2, 3)
>>> matching = nx.bipartite.maximum_matching(G)
>>> vertex_cover = nx.bipartite.to_vertex_cover(G, matching)
>>> independent_set = set(G) - vertex_cover
>>> print(list(independent_set))
[2, 3, 4]
See :mod:`bipartite documentation <networkx.algorithms.bipartite>`
for further details on how bipartite graphs are handled in NetworkX.
"""
# This is a Python implementation of the algorithm described at
# <https://en.wikipedia.org/wiki/K%C3%B6nig%27s_theorem_%28graph_theory%29#Proof>.
L, R = bipartite_sets(G, top_nodes)
# Let U be the set of unmatched vertices in the left vertex set.
unmatched_vertices = set(G) - set(matching)
U = unmatched_vertices & L
# Let Z be the set of vertices that are either in U or are connected to U
# by alternating paths.
Z = _connected_by_alternating_paths(G, matching, U)
# At this point, every edge either has a right endpoint in Z or a left
# endpoint not in Z. This gives us the vertex cover.
return (L - Z) | (R & Z)
def eppstein_matching(G, top_nodes=None):
"""Returns the maximum cardinality matching of the bipartite graph `G`.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
top_nodes : container
Container with all nodes in one bipartite node set. If not supplied
it will be computed. But if more than one solution exists an exception
will be raised.
Returns
-------
matches : dictionary
The matching is returned as a dictionary, `matching`, such that
``matching[v] == w`` if node `v` is matched to node `w`. Unmatched
nodes do not occur as a key in `matching`.
Raises
------
AmbiguousSolution
Raised if the input bipartite graph is disconnected and no container
with all nodes in one bipartite set is provided. When determining
the nodes in each bipartite set more than one valid solution is
possible if the input graph is disconnected.
Notes
-----
This function is implemented with David Eppstein's version of the algorithm
Hopcroft--Karp algorithm (see :func:`hopcroft_karp_matching`), which
originally appeared in the `Python Algorithms and Data Structures library
(PADS) <http://www.ics.uci.edu/~eppstein/PADS/ABOUT-PADS.txt>`_.
See :mod:`bipartite documentation <networkx.algorithms.bipartite>`
for further details on how bipartite graphs are handled in NetworkX.
See Also
--------
hopcroft_karp_matching
"""
# Due to its original implementation, a directed graph is needed
# so that the two sets of bipartite nodes can be distinguished
left, right = bipartite_sets(G, top_nodes)
G = nx.DiGraph(G.edges(left))
# initialize greedy matching (redundant, but faster than full search)
matching = {}
for u in G:
for v in G[u]:
if v not in matching:
matching[v] = u
break
while True:
# structure residual graph into layers
# pred[u] gives the neighbor in the previous layer for u in U
# preds[v] gives a list of neighbors in the previous layer for v in V
# unmatched gives a list of unmatched vertices in final layer of V,
# and is also used as a flag value for pred[u] when u is in the first
# layer
preds = {}
unmatched = []
pred = {u: unmatched for u in G}
for v in matching:
del pred[matching[v]]
layer = list(pred)
# repeatedly extend layering structure by another pair of layers
while layer and not unmatched:
newLayer = {}
for u in layer:
for v in G[u]:
if v not in preds:
newLayer.setdefault(v, []).append(u)
layer = []
for v in newLayer:
preds[v] = newLayer[v]
if v in matching:
layer.append(matching[v])
pred[matching[v]] = v
else:
unmatched.append(v)
# did we finish layering without finding any alternating paths?
if not unmatched:
unlayered = {}
for u in G:
# TODO Why is extra inner loop necessary?
for v in G[u]:
if v not in preds:
unlayered[v] = None
# TODO Originally, this function returned a three-tuple:
#
# return (matching, list(pred), list(unlayered))
#
# For some reason, the documentation for this function
# indicated that the second and third elements of the returned
# three-tuple would be the vertices in the left and right vertex
# sets, respectively, that are also in the maximum independent set.
# However, what I think the author meant was that the second
# element is the list of vertices that were unmatched and the third
# element was the list of vertices that were matched. Since that
# seems to be the case, they don't really need to be returned,
# since that information can be inferred from the matching
# dictionary.
# All the matched nodes must be a key in the dictionary
for key in matching.copy():
matching[matching[key]] = key
return matching
# recursively search backward through layers to find alternating paths
# recursion returns true if found path, false otherwise
def recurse(v):
if v in preds:
L = preds.pop(v)
for u in L:
if u in pred:
pu = pred.pop(u)
if pu is unmatched or recurse(pu):
matching[v] = u
return True
return False
for v in unmatched:
recurse(v)
def hopcroft_karp_matching(G):
"""Returns the maximum cardinality matching of the bipartite graph `G`.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
Returns
-------
matches : dictionary
The matching is returned as a dictionary, `matches`, such that
``matches[v] == w`` if node ``v`` is matched to node ``w``. Unmatched
nodes do not occur as a key in mate.
Notes
-----
This function is implemented with the `Hopcroft--Karp matching algorithm
<https://en.wikipedia.org/wiki/Hopcroft%E2%80%93Karp_algorithm>`_ for
bipartite graphs.
See Also
--------
eppstein_matching
References
----------
.. [1] John E. Hopcroft and Richard M. Karp. "An n^{5 / 2} Algorithm for
Maximum Matchings in Bipartite Graphs" In: **SIAM Journal of Computing**
2.4 (1973), pp. 225--231. <https://dx.doi.org/10.1137/0202019>.
"""
# First we define some auxiliary search functions.
#
# If you are a human reading these auxiliary search functions, the "global"
# variables `leftmatches`, `rightmatches`, `distances`, etc. are defined
# below the functions, so that they are initialized close to the initial
# invocation of the search functions.
def breadth_first_search():
for v in left:
if leftmatches[v] is None:
distances[v] = 0
queue.append(v)
else:
distances[v] = INFINITY
distances[None] = INFINITY
while queue:
v = queue.popleft()
if distances[v] < distances[None]:
for u in G[v]:
if distances[rightmatches[u]] is INFINITY:
distances[rightmatches[u]] = distances[v] + 1
queue.append(rightmatches[u])
return distances[None] is not INFINITY
def depth_first_search(v):
if v is not None:
for u in G[v]:
if distances[rightmatches[u]] == distances[v] + 1:
if depth_first_search(rightmatches[u]):
rightmatches[u] = v
leftmatches[v] = u
return True
distances[v] = INFINITY
return False
return True
# Initialize the "global" variables that maintain state during the search.
left, right = bipartite_sets(G)
leftmatches = {v: None for v in left}
rightmatches = {v: None for v in right}
distances = {}
queue = collections.deque()
# Implementation note: this counter is incremented as pairs are matched but
# it is currently not used elsewhere in the computation.
num_matched_pairs = 0
while breadth_first_search():
for v in left:
if leftmatches[v] is None:
if depth_first_search(v):
num_matched_pairs += 1
# Strip the entries matched to `None`.
leftmatches = {k: v for k, v in leftmatches.items() if v is not None}
rightmatches = {k: v for k, v in rightmatches.items() if v is not None}
# At this point, the left matches and the right matches are inverses of one
# another. In other words,
#
# leftmatches == {v, k for k, v in rightmatches.items()}
#
# Finally, we combine both the left matches and right matches.
return dict(itertools.chain(leftmatches.items(), rightmatches.items()))
def to_vertex_cover(G, matching, top_nodes=None):
"""Returns the minimum vertex cover corresponding to the given maximum
matching of the bipartite graph `G`.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
matching : dictionary
A dictionary whose keys are vertices in `G` and whose values are the
distinct neighbors comprising the maximum matching for `G`, as returned
by, for example, :func:`maximum_matching`. The dictionary *must*
represent the maximum matching.
top_nodes : container
Container with all nodes in one bipartite node set. If not supplied
it will be computed. But if more than one solution exists an exception
will be raised.
Returns
-------
vertex_cover : :class:`set`
The minimum vertex cover in `G`.
Raises
------
AmbiguousSolution : Exception
Raised if the input bipartite graph is disconnected and no container
with all nodes in one bipartite set is provided. When determining
the nodes in each bipartite set more than one valid solution is
possible if the input graph is disconnected.
Notes
-----
This function is implemented using the procedure guaranteed by `Konig's
theorem
<https://en.wikipedia.org/wiki/K%C3%B6nig%27s_theorem_%28graph_theory%29>`_,
which proves an equivalence between a maximum matching and a minimum vertex
cover in bipartite graphs.
Since a minimum vertex cover is the complement of a maximum independent set
for any graph, one can compute the maximum independent set of a bipartite
graph this way:
>>> import networkx as nx
>>> G = nx.complete_bipartite_graph(2, 3)
>>> matching = nx.bipartite.maximum_matching(G)
>>> vertex_cover = nx.bipartite.to_vertex_cover(G, matching)
>>> independent_set = set(G) - vertex_cover
>>> print(list(independent_set))
[2, 3, 4]
See :mod:`bipartite documentation <networkx.algorithms.bipartite>`
for further details on how bipartite graphs are handled in NetworkX.
"""
# This is a Python implementation of the algorithm described at
# <https://en.wikipedia.org/wiki/K%C3%B6nig%27s_theorem_%28graph_theory%29#Proof>.
L, R = bipartite_sets(G, top_nodes)
# Let U be the set of unmatched vertices in the left vertex set.
unmatched_vertices = set(G) - set(matching)
U = unmatched_vertices & L
# Let Z be the set of vertices that are either in U or are connected to U
# by alternating paths.
Z = _connected_by_alternating_paths(G, matching, U)
# At this point, every edge either has a right endpoint in Z or a left
# endpoint not in Z. This gives us the vertex cover.
return (L - Z) | (R & Z)
def eppstein_matching(G, top_nodes=None):
"""Returns the maximum cardinality matching of the bipartite graph `G`.
Parameters
----------
G : NetworkX graph
Undirected bipartite graph
top_nodes : container
Container with all nodes in one bipartite node set. If not supplied
it will be computed. But if more than one solution exists an exception
will be raised.
Returns
-------
matches : dictionary
The matching is returned as a dictionary, `matching`, such that
``matching[v] == w`` if node `v` is matched to node `w`. Unmatched
nodes do not occur as a key in mate.
Raises
------
AmbiguousSolution : Exception
Raised if the input bipartite graph is disconnected and no container
with all nodes in one bipartite set is provided. When determining
the nodes in each bipartite set more than one valid solution is
possible if the input graph is disconnected.
Notes
-----
This function is implemented with David Eppstein's version of the algorithm
Hopcroft--Karp algorithm (see :func:`hopcroft_karp_matching`), which
originally appeared in the `Python Algorithms and Data Structures library
(PADS) <http://www.ics.uci.edu/~eppstein/PADS/ABOUT-PADS.txt>`_.
See :mod:`bipartite documentation <networkx.algorithms.bipartite>`
for further details on how bipartite graphs are handled in NetworkX.
See Also
--------
hopcroft_karp_matching
"""
# Due to its original implementation, a directed graph is needed
# so that the two sets of bipartite nodes can be distinguished
left, right = bipartite_sets(G, top_nodes)
G = nx.DiGraph(G.edges(left))
# initialize greedy matching (redundant, but faster than full search)
matching = {}
for u in G:
for v in G[u]:
if v not in matching:
matching[v] = u
break
while True:
# structure residual graph into layers
# pred[u] gives the neighbor in the previous layer for u in U
# preds[v] gives a list of neighbors in the previous layer for v in V
# unmatched gives a list of unmatched vertices in final layer of V,
# and is also used as a flag value for pred[u] when u is in the first
# layer
preds = {}
unmatched = []
pred = {u: unmatched for u in G}
for v in matching:
del pred[matching[v]]
layer = list(pred)
# repeatedly extend layering structure by another pair of layers
while layer and not unmatched:
newLayer = {}
for u in layer:
for v in G[u]:
if v not in preds:
newLayer.setdefault(v, []).append(u)
layer = []
for v in newLayer:
preds[v] = newLayer[v]
if v in matching:
layer.append(matching[v])
pred[matching[v]] = v
else:
unmatched.append(v)
# did we finish layering without finding any alternating paths?
if not unmatched:
unlayered = {}
for u in G:
# TODO Why is extra inner loop necessary?
for v in G[u]:
if v not in preds:
unlayered[v] = None
# TODO Originally, this function returned a three-tuple:
#
# return (matching, list(pred), list(unlayered))
#
# For some reason, the documentation for this function
# indicated that the second and third elements of the returned
# three-tuple would be the vertices in the left and right vertex
# sets, respectively, that are also in the maximum independent set.
# However, what I think the author meant was that the second
# element is the list of vertices that were unmatched and the third
# element was the list of vertices that were matched. Since that
# seems to be the case, they don't really need to be returned,
# since that information can be inferred from the matching
# dictionary.
# All the matched nodes must be a key in the dictionary
for key in matching.copy():
matching[matching[key]] = key
return matching
# recursively search backward through layers to find alternating paths
# recursion returns true if found path, false otherwise
def recurse(v):
if v in preds:
L = preds.pop(v)
for u in L:
if u in pred:
pu = pred.pop(u)
if pu is unmatched or recurse(pu):
matching[v] = u
return True
return False
for v in unmatched:
recurse(v)
import networkx
from networkx.algorithms import bipartite
# Create the actor/movie graph
g = networkx.Graph()
g.add_edges_from([("Stallone", "Expendables"), ("Schwarzenegger", "Expendables")])
g.add_edges_from([("Schwarzenegger", "Terminator 2"), ("Furlong", "Terminator 2")])
g.add_edges_from([("Furlong", "Green Hornet"), ("Diaz", "Green Hornet")])
# Test if graph is bipartite
print bipartite.is_bipartite(g)
print bipartite.bipartite_sets(g)
# Graph is no longer bipartite after this
g.add_edge("Schwarzenegger", "Stallone")
print bipartite.is_bipartite(g)
import networkx
from networkx.algorithms import bipartite
# Create the actor/movie graph
g = networkx.Graph()
g.add_edges_from([("Stallone", "Expendables"),
("Schwarzenegger", "Expendables")])
g.add_edges_from([("Schwarzenegger", "Terminator 2"),
("Furlong", "Terminator 2")])
g.add_edges_from([("Furlong", "Green Hornet"), ("Diaz", "Green Hornet")])
# Test if graph is bipartite
print bipartite.is_bipartite(g)
print bipartite.bipartite_sets(g)
# Graph is no longer bipartite after this
g.add_edge("Schwarzenegger", "Stallone")
print bipartite.is_bipartite(g)
