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" This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges). "
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" # Challenge Notebook "
]
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" ## Problem: Implement a function to reverse a string (a list of characters), in-place. \n " ,
" \n " ,
" * [Constraints](#Constraints) \n " ,
" * [Test Cases](#Test-Cases) \n " ,
" * [Algorithm](#Algorithm) \n " ,
" * [Code](#Code) \n " ,
" * [Unit Test](#Unit-Test) \n " ,
" * [Solution Notebook](#Solution-Notebook) "
]
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" ## Constraints \n " ,
" \n " ,
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" * Can we assume the string is ASCII? \n " ,
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" * Yes \n " ,
" * Note: Unicode strings could require special handling depending on your language \n " ,
" * Since we need to do this in-place, it seems we cannot use the slice operator or the reversed function? \n " ,
" * Correct \n " ,
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" * Since Python string are immutable, can we use a list of characters instead? \n " ,
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" * Yes "
]
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" ## Test Cases \n " ,
" \n " ,
" * None -> None \n " ,
" * [ ' ' ] -> [ ' ' ] \n " ,
" * [ ' f ' , ' o ' , ' o ' , ' ' , ' b ' , ' a ' , ' r ' ] -> [ ' r ' , ' a ' , ' b ' , ' ' , ' o ' , ' o ' , ' f ' ] "
]
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" ## Algorithm \n " ,
" \n " ,
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" Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_solution.ipynb). If you are stuck and need a hint, the solution notebook ' s algorithm discussion might be a good place to start. "
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]
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" ## Code "
]
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" class ReverseString(object): \n " ,
" \n " ,
" def reverse(self, chars): \n " ,
" # TODO: Implement me \n " ,
" pass "
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]
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" ## Unit Test "
]
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" \n " ,
" \n " ,
" **The following unit test is expected to fail until you solve the challenge.** "
]
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" # %lo ad test_reverse_string.py \n " ,
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" import unittest \n " ,
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" \n " ,
" \n " ,
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" class TestReverse(unittest.TestCase): \n " ,
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" \n " ,
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" def test_reverse(self, func): \n " ,
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" self.assertEqual(func(None), None) \n " ,
" self.assertEqual(func([ ' ' ]), [ ' ' ]) \n " ,
" self.assertEqual(func( \n " ,
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" [ ' f ' , ' o ' , ' o ' , ' ' , ' b ' , ' a ' , ' r ' ]), \n " ,
" [ ' r ' , ' a ' , ' b ' , ' ' , ' o ' , ' o ' , ' f ' ]) \n " ,
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" print( ' Success: test_reverse ' ) \n " ,
" \n " ,
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" def test_reverse_inplace(self, func): \n " ,
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" target_list = [ ' f ' , ' o ' , ' o ' , ' ' , ' b ' , ' a ' , ' r ' ] \n " ,
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" func(target_list) \n " ,
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" self.assertEqual(target_list, [ ' r ' , ' a ' , ' b ' , ' ' , ' o ' , ' o ' , ' f ' ]) \n " ,
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" print( ' Success: test_reverse_inplace ' ) \n " ,
" \n " ,
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" \n " ,
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" def main(): \n " ,
" test = TestReverse() \n " ,
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" reverse_string = ReverseString() \n " ,
" test.test_reverse(reverse_string.reverse) \n " ,
" test.test_reverse_inplace(reverse_string.reverse) \n " ,
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" \n " ,
" \n " ,
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" if __name__ == ' __main__ ' : \n " ,
" main() "
]
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" cell_type " : " markdown " ,
" metadata " : { } ,
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" ## Solution Notebook \n " ,
" \n " ,
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" Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_solution.ipynb) for a discussion on algorithms and code solutions. "
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]
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