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import unittest
def reverse(xs, i, j):
"""Reverse array of characters, xs, in-place."""
while i < j:
xs[i], xs[j] = xs[j], xs[i]
i += 1
j -= 1
def reverse_words(xs):
reverse(xs, 0, len(xs) - 1)
i = 0
j = i
while j < len(xs):
while j < len(xs) and xs[j] != ' ':
j += 1
reverse(xs, i, j - 1)
j += 1
i = j
# Tests
class Test(unittest.TestCase):
def test_one_word(self):
message = list('vault')
reverse_words(message)
expected = list('vault')
self.assertEqual(message, expected)
def test_two_words(self):
message = list('thief cake')
reverse_words(message)
expected = list('cake thief')
self.assertEqual(message, expected)
def test_three_words(self):
message = list('one another get')
reverse_words(message)
expected = list('get another one')
self.assertEqual(message, expected)
def test_multiple_words_same_length(self):
message = list('rat the ate cat the')
reverse_words(message)
expected = list('the cat ate the rat')
self.assertEqual(message, expected)
def test_multiple_words_different_lengths(self):
message = list('yummy is cake bundt chocolate')
reverse_words(message)
expected = list('chocolate bundt cake is yummy')
self.assertEqual(message, expected)
def test_empty_string(self):
message = list('')
reverse_words(message)
expected = list('')
self.assertEqual(message, expected)
unittest.main(verbosity=2)
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