def count_possible_astronaut_pairs(total_astronauts, astronauts_connections):
"""
Get number of possible astronaut pairs where both of them are
from different countries
"""
graph = UndirectedGraph()
for astronaut in range(0, total_astronauts):
graph.add_vertex(astronaut)
for connection in astronauts_connections:
graph.add_edge(connection[0], connection[1], 0)
country_by_astronaut = vertices_to_components(graph)
count_by_country = {}
for astronaut, country in country_by_astronaut.items():
count_by_country[country] = count_by_country.get(country, 0) + 1
total = 0
pairs = 0
for country, count in count_by_country.items():
pairs += total * count
total += count
return pairs
def test_returns_true_for_graph_without_edges(self):
g = UndirectedGraph()
g.add_vertex(1)
g.add_vertex(2)
g.add_vertex(3)
self.assertTrue(is_bipartite(g))
def test_returns_true_for_graph_with_single_vertex(self):
g = UndirectedGraph()
g.add_vertex(1)
self.assertTrue(is_bipartite(g))