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import unittest
from itertools import permutations
class Node(object):
def __init__(self, x):
self.value = x
self.children = []
def make_tree(c, xs):
root = Node(c)
for x in xs:
root.children.append(make_tree(x, xs - {x}))
return root
def get_permutations(xs):
xs = set(xs)
root = make_tree("", xs)
q, perms = [], set()
q.append(("", root))
while q:
c, node = q.pop()
if not node.children:
perms.add(c)
else:
for child in node.children:
q.append((c + child.value, child))
return perms
# Tests
class Test(unittest.TestCase):
def test_empty_string(self):
actual = get_permutations('')
expected = set([''])
self.assertEqual(actual, expected)
def test_one_character_string(self):
actual = get_permutations('a')
expected = set(['a'])
self.assertEqual(actual, expected)
def test_two_character_string(self):
actual = get_permutations('ab')
expected = set(['ab', 'ba'])
self.assertEqual(actual, expected)
def test_three_character_string(self):
actual = get_permutations('abc')
expected = set(['abc', 'acb', 'bac', 'bca', 'cab', 'cba'])
self.assertEqual(actual, expected)
unittest.main(verbosity=2)
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