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rail-fence-cipher: Implement new exercise #273

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Merged
Dog merged 1 commit into from
Jul 21, 2016
Merged

rail-fence-cipher: Implement new exercise #273

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1 change: 1 addition & 0 deletions config.json
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@
"pythagorean-triplet",
"robot-name",
"matrix",
"rail-fence-cipher",
"nth-prime",
"saddle-points",
"beer-song",
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17 changes: 17 additions & 0 deletions rail-fence-cipher/example.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
from itertools import cycle, chain


def fence_pattern(rails, size):
zig_zag = cycle(chain(range(rails), range(rails - 2, 0, -1)))
return zip(zig_zag, range(size))


def encode(msg, rails):
fence = fence_pattern(rails, len(msg))
return ''.join(msg[i] for _, i in sorted(fence))


def decode(msg, rails):
fence = fence_pattern(rails, len(msg))
fence_msg = zip(msg, sorted(fence))
return ''.join(char for char, _ in sorted(fence_msg, key=lambda item: item[1][1]))
34 changes: 34 additions & 0 deletions rail-fence-cipher/rail_fence_cipher_test.py
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import unittest

from rail_fence_cipher import encode, decode


class RailFenceTests(unittest.TestCase):

def test_encode_with_two_rails(self):
self.assertMultiLineEqual('XXXXXXXXXOOOOOOOOO',
encode('XOXOXOXOXOXOXOXOXO', 2))

def test_encode_with_three_rails(self):
self.assertMultiLineEqual('WECRLTEERDSOEEFEAOCAIVDEN',
encode('WEAREDISCOVEREDFLEEATONCE', 3))

def test_encode_with_middle_stop(self):
self.assertMultiLineEqual('ESXIEECSR', encode('EXERCISES', 4))

def test_decode_with_three_rails(self):
self.assertMultiLineEqual('THEDEVILISINTHEDETAILS',
decode('TEITELHDVLSNHDTISEIIEA', 3))

def test_decode_with_five_rails(self):
self.assertMultiLineEqual('EXERCISMISAWESOME',
decode('EIEXMSMESAORIWSCE', 5))

def test_decode_with_six_rails(self):
self.assertMultiLineEqual(
'112358132134558914423337761098715972584418167651094617711286',
decode('133714114238148966225439541018335470986172518171757571896261', 6)
)

if __name__ == '__main__':
unittest.main()