def test_find_shortest_paths_bfs(self):
graph = DirectedGraph()
edges = [ # https://cs.stackexchange.com/questions/18138/dijkstra-algorithm-vs-breadth-first-search-for-shortest-path-in-graph
('A', 'B', 1),
('B', 'C', 1),
('B', 'D', 1),
('B', 'E', 1),
('C', 'E', 1),
('D', 'E', 1),
('E', 'F', 1),
('G', 'D', 1),
]
for src, des, weight in edges:
graph.add_edge(src, des, weight)
previous, distances = graph.find_shortest_paths_bfs('A')
path = graph.construct_path(previous, 'A', 'E')
self.assertEqual(path, ['A', 'B', 'E'])
path = graph.construct_path(previous, 'A', 'D')
self.assertEqual(path, ['A', 'B', 'D'])
# No such path.
with self.assertRaises(ValueError):
graph.construct_path(previous, 'A', 'G')
def test_find_shortest_paths_bfs(self):
graph = DirectedGraph()
edges = [ # https://www.geeksforgeeks.org/shortest-path-unweighted-graph/
(0, 1, 1),
(0, 3, 1),
(1, 0, 1),
(1, 2, 1),
(2, 1, 1),
(3, 0, 1),
(3, 4, 1),
(3, 7, 1),
(4, 3, 1),
(4, 5, 1),
(4, 6, 1),
(4, 7, 1),
(5, 4, 1),
(5, 6, 1),
(6, 4, 1),
(6, 5, 1),
(6, 7, 1),
(7, 3, 1),
(7, 4, 1),
(7, 6, 1),
]
for src, des, weight in edges:
graph.add_edge(src, des, weight)
previous, distances = graph.find_shortest_paths_bfs(0)
path = graph.construct_path(previous, 0, 5)
self.assertEqual(path, [0, 3, 4, 5])
path = graph.construct_path(previous, 0, 7)
self.assertEqual(path, [0, 3, 7])
# No such path.
with self.assertRaises(ValueError):
graph.construct_path(previous, 0, 10)