def main():
"""Unit tests the DirectedDFS data type."""
G = Digraph.from_stream(InStream(None))
sources = Bag()
for i in range(1, len(sys.argv)):
s = int(sys.argv[i])
sources.add(s)
dfs = DirectedDFS(G, *sources)
print("Reachable vertices:")
for v in range(0, G.V()):
if dfs.is_marked(v):
print(v, end=" ")
print()
def main(args):
stream = InStream(args[0])
G = Digraph.from_stream(stream)
scc = KosarajuSharirSCC(G)
# number of connected components
m = scc.count()
print("{} strong components".format(m))
# compute list of vertices in each strong component
components = [Queue() for i in range(m)]
for v in range(G.V()):
components[scc.id(v)].enqueue(v)
# print results
for i in range(m):
for v in components[i]:
print(str(v), end=" ")
print()
def main(args):
stream = InStream(args[0])
G = Digraph.from_stream(stream)
tc = TransitiveClosure(G)
# print header
print(" ", end="")
for v in range(G.V()):
print("{x:3d}".format(x=v), end="")
print()
print("--------------------------------------------")
# print transitive closure
for v in range(G.V()):
print("{x:3d}: ".format(x=v), end="")
for w in range(G.V()):
if tc.reachable(v, w):
print(" T", end="")
else:
print(" ", end="")
print()
self._on_stack[v] = False
def has_cycle(self):
"""Does the digraph have a directed cycle?
:returns: true if there is a cycle, false otherwise
"""
return self._cycle is not None
def cycle(self):
"""Returns a directed cycle if the digraph has a directed cycle, and
null otherwise.
:returns: a directed cycle (as an iterable) if the digraph has a directed cycle, and null otherwise
"""
return self._cycle
if __name__ == "__main__":
# Create stream from file or the standard input,
# depending on whether a file name was passed.
stream = sys.argv[1] if len(sys.argv) > 1 else None
d = Digraph.from_stream(InStream(stream))
cyc = DirectedCycle(d)
print(cyc.cycle())