def test_initialization(self):
"""Test public methods on an empty union."""
# Create { }.
an_empty_graph = UnionFind()
self.assertEqual(an_empty_graph.n_vertices(), 0)
self.assertEqual(an_empty_graph.connected(0, 0), False)
self.assertEqual(an_empty_graph.connected(0, 1), False)
def test_non_consecutive_adding(self):
"""Test adding vertices non-consecutively."""
# Create { }.
a_graph = UnionFind()
# Add 1 to { }, which becomes { {0}, {1} }.
# Here 0 is added implicitly.
a_graph.add(1)
self.assertEqual(a_graph.n_vertices(), 2)
self.assertEqual(a_graph.connected(0, 0), True)
self.assertEqual(a_graph.connected(0, 1), False)
self.assertEqual(a_graph.connected(1, 1), True)
def test_consecutive_adding(self):
"""Test adding vertices consecutively."""
# Create { }.
a_graph = UnionFind()
# Add 0 to { }, which becomes { {0} }.
a_graph.add(0)
self.assertEqual(a_graph.n_vertices(), 1)
self.assertEqual(a_graph.connected(0, 0), True)
self.assertEqual(a_graph.connected(0, 1), False)
self.assertEqual(a_graph.connected(1, 1), False)
# Add 0 to { {0} }, nothing changes.
a_graph.add(0)
self.assertEqual(a_graph.n_vertices(), 1)
self.assertEqual(a_graph.connected(0, 0), True)
self.assertEqual(a_graph.connected(0, 1), False)
self.assertEqual(a_graph.connected(1, 1), False)
# Add 1 to { {0} }, which becomes { {0}, {1} }.
a_graph.add(1)
self.assertEqual(a_graph.n_vertices(), 2)
self.assertEqual(a_graph.connected(0, 0), True)
self.assertEqual(a_graph.connected(0, 1), False)
self.assertEqual(a_graph.connected(1, 1), True)
def test_implicit_adding_by_connecting(self):
"""Test connect(), which implicitly calls add()."""
# Create { }.
a_graph = UnionFind()
# Implicitly add 0, 1, 2 to { }, then connect 1 with 2,
# which makes { {0}, {1, 2} }.
a_graph.connect(1, 2)
self.assertEqual(a_graph.n_vertices(), 3)
# Trivially connected components.
self.assertEqual(a_graph.connected(0, 0), True)
self.assertEqual(a_graph.connected(1, 1), True)
self.assertEqual(a_graph.connected(2, 2), True)
# Connected components created by connect().
self.assertEqual(a_graph.connected(1, 2), True)
self.assertEqual(a_graph.connected(2, 1), True)
# Disconnected components.
self.assertEqual(a_graph.connected(0, 1), False)
self.assertEqual(a_graph.connected(1, 0), False)
self.assertEqual(a_graph.connected(0, 2), False)
self.assertEqual(a_graph.connected(2, 0), False)