019f8fd211
git-subtree-dir: users/wpcarro git-subtree-mainline:464bbcb15cgit-subtree-split:24f5a642afChange-Id: I6105b3762b79126b3488359c95978cadb3efa789
83 lines
1.9 KiB
Python
83 lines
1.9 KiB
Python
import unittest
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################################################################################
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# Answer
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################################################################################
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class Node(object):
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def __init__(self, value, children=set()):
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self.value = value
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self.children = children
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# treeify :: Char -> Set(Char) -> Node(Char)
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def treeify(x, xs):
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return Node(x, [treeify(c, xs - {c}) for c in xs])
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# dft :: Node(Char) -> [String]
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def dft(node):
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result = []
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s = []
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s.append(('', node))
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while s:
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p, n = s.pop()
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p += str(n.value)
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if not n.children:
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result.append(p)
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else:
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for c in n.children:
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s.append((p, c))
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return result
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# main :: String -> Set(String)
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def get_permutations(xs):
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if xs == '':
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return set([''])
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ys = set(xs)
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trees = []
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for y in ys:
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trees.append(treeify(y, ys - {y}))
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result = set()
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for t in trees:
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for d in dft(t):
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result.add(d)
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return result
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################################################################################
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# Tests
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################################################################################
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class Test(unittest.TestCase):
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def test_empty_string(self):
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actual = get_permutations('')
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expected = set([''])
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self.assertEqual(actual, expected)
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def test_one_character_string(self):
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actual = get_permutations('a')
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expected = set(['a'])
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self.assertEqual(actual, expected)
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def test_two_character_string(self):
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actual = get_permutations('ab')
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expected = set(['ab', 'ba'])
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self.assertEqual(actual, expected)
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def test_three_character_string(self):
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actual = get_permutations('abc')
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expected = set(['abc', 'acb', 'bac', 'bca', 'cab', 'cba'])
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self.assertEqual(actual, expected)
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unittest.main(verbosity=2)
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