This notebook was prepared by Donne Martin. Source and license info is on GitHub.

# Challenge Notebook¶

## Constraints¶

• Can we assume the inputs are valid?
• No
• Can we assume the strings are ASCII?
• Yes
• Is this case sensitive?
• Yes
• Is a subsequence a non-contiguous block of chars?
• Yes
• Do we expect a string as a result?
• Yes
• Can we assume this fits memory?
• Yes

## Test Cases¶

• str0 or str1 is None -> Exception
• str0 or str1 equals 0 -> ''
• General case

str0 = 'ABCDEFGHIJ' str1 = 'FOOBCDBCDE'

result: 'BCDE'

## Algorithm¶

Refer to the Solution Notebook. If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.

## Code¶

In [ ]:
class StringCompare(object):

def longest_common_subseq(self, str0, str1):
# TODO: Implement me
pass


## Unit Test¶

The following unit test is expected to fail until you solve the challenge.

In [ ]:
# %load test_longest_common_subseq.py
import unittest

class TestLongestCommonSubseq(unittest.TestCase):

def test_longest_common_subseq(self):
str_comp = StringCompare()
self.assertRaises(TypeError, str_comp.longest_common_subseq, None, None)
self.assertEqual(str_comp.longest_common_subseq('', ''), '')
str0 = 'ABCDEFGHIJ'
str1 = 'FOOBCDBCDE'
expected = 'BCDE'
self.assertEqual(str_comp.longest_common_subseq(str0, str1), expected)
print('Success: test_longest_common_subseq')

def main():
test = TestLongestCommonSubseq()
test.test_longest_common_subseq()

if __name__ == '__main__':
main()


## Solution Notebook¶

Review the Solution Notebook for a discussion on algorithms and code solutions.