def run(self):
"""Executable pseudocode."""
order = list()
algorithm = SimpleBFS(self.graph)
algorithm.run(pre_action=lambda node: order.append(node))
for source in order:
self._greedy_color(source)
def run(self):
"""Executable pseudocode."""
n = self.graph.v()
e = self.graph.e() # this may be O(E)
if n < 4:
raise ValueError("the number of nodes is less then 4")
elif n == 4 and e == 6: # complete graph K4
self.hub = next(self.graph.iternodes())
return
if e != 2 * n - 2:
raise ValueError("bad number of edges")
dset = set(self.graph.degree(node) for node in self.graph.iternodes())
if dset != set([3, n - 1]):
raise ValueError("bad set of node degrees")
self.hub = max(self.graph.iternodes(), key=self.graph.degree)
# Remove edges from the hub.
removed = list(self.graph.iteroutedges(self.hub))
for edge in removed:
self.graph.del_edge(edge)
# Now a cycle should be present.
# Choose a node different from the hub.
for node in self.graph.iternodes():
if node != self.hub:
source = node
break
order = []
algorithm = SimpleBFS(self.graph)
algorithm.run(source, pre_action=lambda node: order.append(node))
# Restore edges.
for edge in removed:
self.graph.add_edge(edge)
if len(order) != n - 1:
raise ValueError("not a wheel graph")
def run(self):
"""Executable pseudocode."""
n = self.graph.v()
e = self.graph.e() # this may be O(E)
if n < 4:
raise ValueError("the number of nodes is less then 4")
elif n == 4 and e == 6: # complete graph K4
self.hub = next(self.graph.iternodes())
return
if e != 2 * n - 2:
raise ValueError("bad number of edges")
dset = set(self.graph.degree(node) for node in self.graph.iternodes())
if dset != set([3, n-1]):
raise ValueError("bad set of node degrees")
self.hub = max(self.graph.iternodes(), key=self.graph.degree)
# Remove edges from the hub.
removed = list(self.graph.iteroutedges(self.hub))
for edge in removed:
self.graph.del_edge(edge)
# Now a cycle should be present.
# Choose a node different from the hub.
for node in self.graph.iternodes():
if node != self.hub:
source = node
break
order = []
algorithm = SimpleBFS(self.graph)
algorithm.run(source, pre_action=lambda node: order.append(node))
# Restore edges.
for edge in removed:
self.graph.add_edge(edge)
if len(order) != n-1:
raise ValueError("not a wheel graph")
def run(self):
"""Executable pseudocode."""
order = list()
algorithm = SimpleBFS(self.graph)
algorithm.run(pre_action=lambda node: order.append(node))
for source in order:
self._greedy_color(source)
def run(self):
"""Executable pseudocode."""
algorithm = SimpleBFS(self.graph)
for source in self.graph.iternodes():
if self.cc[source] is None:
algorithm.run(source, pre_action=lambda node:
self.cc.__setitem__(node, self.n_cc))
self.n_cc += 1
def _is_bridge(self, edge):
"""Bridge test."""
list1 = list()
list2 = list()
algorithm = SimpleBFS(self._graph_copy)
algorithm.run(edge.source, pre_action=lambda node: list1.append(node))
self._graph_copy.del_edge(edge)
algorithm = SimpleBFS(self._graph_copy)
algorithm.run(edge.source, pre_action=lambda node: list2.append(node))
# Restore the edge.
self._graph_copy.add_edge(edge)
return len(list1) != len(list2)
def test_simple_bfs(self):
self.assertEqual(self.G.v(), self.N)
pre_order = []
post_order = []
algorithm = SimpleBFS(self.G)
algorithm.run(1, pre_action=lambda node: pre_order.append(node),
post_action=lambda node: post_order.append(node))
order_expected = [1, 0, 5, 4, 2, 6, 3, 7]
self.assertEqual(pre_order, order_expected)
self.assertEqual(post_order, order_expected)
parent_expected = {0: 1, 1: None, 2: 5, 3: 2, 4: 0, 5: 1, 6: 5, 7: 6}
self.assertEqual(algorithm.parent, parent_expected)
self.assertEqual(algorithm.path(1, 7), [1, 5, 6, 7])
self.assertEqual(algorithm.path(1, 4), [1, 0, 4])
self.assertRaises(ValueError, algorithm.path, 4, 7)
#algorithm.dag.show()
self.assertEqual(algorithm.dag.v(), self.N)
self.assertEqual(algorithm.dag.e(), self.N-1)
self.assertTrue(algorithm.dag.is_directed())
for edge in algorithm.dag.iteredges():
self.assertTrue(self.G.has_edge(edge))
self.assertEqual(edge.weight, self.G.weight(edge))
def test_simple_bfs(self):
self.assertEqual(self.G.v(), self.N)
pre_order = []
post_order = []
algorithm = SimpleBFS(self.G)
algorithm.run(1,
pre_action=lambda node: pre_order.append(node),
post_action=lambda node: post_order.append(node))
order_expected = [1, 0, 5, 4, 2, 6, 3, 7]
self.assertEqual(pre_order, order_expected)
self.assertEqual(post_order, order_expected)
parent_expected = {0: 1, 1: None, 2: 5, 3: 2, 4: 0, 5: 1, 6: 5, 7: 6}
self.assertEqual(algorithm.parent, parent_expected)
self.assertEqual(algorithm.path(1, 7), [1, 5, 6, 7])
self.assertEqual(algorithm.path(1, 4), [1, 0, 4])
self.assertRaises(ValueError, algorithm.path, 4, 7)
#algorithm.dag.show()
self.assertEqual(algorithm.dag.v(), self.N)
self.assertEqual(algorithm.dag.e(), self.N - 1)
self.assertTrue(algorithm.dag.is_directed())
for edge in algorithm.dag.iteredges():
self.assertTrue(self.G.has_edge(edge))
self.assertEqual(edge.weight, self.G.weight(edge))
def _is_bridge(self, edge):
"""Bridge test."""
list1 = list()
list2 = list()
algorithm = SimpleBFS(self._graph_copy)
algorithm.run(edge.source, pre_action=lambda node: list1.append(node))
self._graph_copy.del_edge(edge)
algorithm = SimpleBFS(self._graph_copy)
algorithm.run(edge.source, pre_action=lambda node: list2.append(node))
# Restore the edge.
self._graph_copy.add_edge(edge)
return len(list1) != len(list2)
def run(self):
"""Executable pseudocode."""
for source in self.graph.iternodes():
algorithm = SimpleBFS(self.graph)
algorithm.run(source, pre_action=lambda node:
self.T[source].__setitem__(node, True))
