return topological_list
def dfs_visit(graph: Graph, u: Any, time: int, status: dict,
topological_list: LinkedList) -> None:
"""
Completely explores each vertex connected to the source vertex u, starting from lowest depth
:param graph: the graph to perform dfs_visit on
:param u: the vertex to recurse down
:param time: the time called
:return: the time after dfs_visit() completes on the source vertex
"""
status[u] = 1 # update u to grey
time += 1
for v in graph.adjacency_list[u]:
if status[v] == 0:
dfs_visit(graph, v, time, status, topological_list)
status[u] = 2
time += 1
topological_list.insert_first(u)
if __name__ == '__main__':
graph = DirectedGraph()
graph.add_vertices(["a", "b", "c", "d", "e", "f"])
graph.add_edges([("a", "b"), ("a", "d"), ("b", "e"), ("c", "f"),
("d", "b"), ("f", "d")])
print(graph)
print(topological_sort(graph))
:return: the time after dfs_visit() completes on the source vertex
"""
status[u] = 1 # update u to grey
time += 1
discovery_time[u] = time
for v in graph.adjacency_list[u]:
if status[v] == 0:
parent[v] = u
time = dfs_visit(graph, v, time, status, discovery_time,
finish_time, parent)
status[u] = 2
time += 1
finish_time[u] = time
return time
if __name__ == '__main__':
graph1 = DirectedGraph()
graph1.add_vertices([1, 2, 3, 4, 5, 6, 7])
graph1.add_edges([(1, 2), (1, 4), (1, 7), (2, 3), (2, 4), (3, 1), (3, 4),
(5, 4), (5, 6), (6, 3), (6, 5), (7, 1), (7, 4)])
print(graph1)
print(str(dfs(graph1)) + "\n")
graph2 = DirectedGraph()
graph2.add_vertices(["a", "b", "c", "d", "e", "f"])
graph2.add_edges([("a", "b"), ("a", "d"), ("b", "e"), ("c", "f"),
("d", "b"), ("e", "d"), ("f", "d"), ("f", "f")])
print(graph2)
print(dfs(graph2))
parent[vertex] = None
status[
source] = 1 # initialize source at grey (visited but not explored completely)
distance[source] = 0 # the distance from the source to itself is 0
q = Queue() # queue for vertices that need to be explored
q.enqueue(source)
while not q.is_empty():
u = q.dequeue()
for v in graph.adjacency_list[u]:
if status[v] == 0: # if vertex v is white
status[v] = 1 # update v to grey
distance[v] = distance[u] + 1
parent[v] = u
q.enqueue(v)
status[u] = 2 # we have fully explored u, hence update u to black
bfs_traversal.append((u, distance[u], parent[u]))
return bfs_traversal
if __name__ == '__main__':
graph = DirectedGraph()
graph.add_vertices(["s", "a", "b", "c", "d", "e", "f"])
graph.add_edges([("s", "a"), ("s", "f"), ("a", "b"), ("a", "e"),
("b", "c"), ("b", "d"), ("c", "d"), ("c", "e"),
("e", "d"), ("e", "f")])
print(graph)
print(bfs(graph, "s"))
