import unittest
from collections import deque
################################################################################
# Solution
################################################################################
# get_path :: G(V, E) -> V -> V -> Maybe([V])
def get_path(g, src, dst):
q = deque()
result = None
seen = set()
q.append(([], src))
if src not in g or dst not in g:
raise Exception
while q:
p, node = q.popleft()
seen.add(node)
if node == dst:
if not result:
result = p + [node]
elif len(p + [node]) < len(result):
result = p + [node]
else:
if node not in g:
raise Exception
for x in g.get(node):
if not x in seen:
q.append((p + [node], x))
return result
################################################################################
# Tests
################################################################################
class Test(unittest.TestCase):
def setUp(self):
self.graph = {
'a': ['b', 'c', 'd'],
'b': ['a', 'd'],
'c': ['a', 'e'],
'd': ['a', 'b'],
'e': ['c'],
'f': ['g'],
'g': ['f'],
}
def test_two_hop_path_1(self):
actual = get_path(self.graph, 'a', 'e')
expected = ['a', 'c', 'e']
self.assertEqual(actual, expected)
def test_two_hop_path_2(self):
actual = get_path(self.graph, 'd', 'c')
expected = ['d', 'a', 'c']
self.assertEqual(actual, expected)
def test_one_hop_path_1(self):
actual = get_path(self.graph, 'a', 'c')
expected = ['a', 'c']
self.assertEqual(actual, expected)
def test_one_hop_path_2(self):
actual = get_path(self.graph, 'f', 'g')
expected = ['f', 'g']
self.assertEqual(actual, expected)
def test_one_hop_path_3(self):
actual = get_path(self.graph, 'g', 'f')
expected = ['g', 'f']
self.assertEqual(actual, expected)
def test_zero_hop_path(self):
actual = get_path(self.graph, 'a', 'a')
expected = ['a']
self.assertEqual(actual, expected)
def test_no_path(self):
actual = get_path(self.graph, 'a', 'f')
expected = None
self.assertEqual(actual, expected)
def test_start_node_not_present(self):
with self.assertRaises(Exception):
get_path(self.graph, 'h', 'a')
def test_end_node_not_present(self):
with self.assertRaises(Exception):
get_path(self.graph, 'a', 'h')
unittest.main(verbosity=2)
