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 substring a contiguous block of chars?
• Yes
• Do we expect an int as a result?
• Yes
• Can we assume this fits memory?
• Yes

## Test Cases¶

• None -> TypeError
• '', k = 3 -> 0
• 'abcabcdefgghiij', k=3 -> 6
• 'abcabcdefgghighij', k=3 -> 7

## 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 Solution(object):

def longest_substr(self, string, k):
# TODO: Implement me
pass


## Unit Test¶

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

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

class TestSolution(unittest.TestCase):

def test_longest_substr(self):
solution = Solution()
self.assertRaises(TypeError, solution.longest_substr, None)
self.assertEqual(solution.longest_substr('', k=3), 0)
self.assertEqual(solution.longest_substr('abcabcdefgghiij', k=3), 6)
self.assertEqual(solution.longest_substr('abcabcdefgghighij', k=3), 7)
print('Success: test_longest_substr')

def main():
test = TestSolution()
test.test_longest_substr()

if __name__ == '__main__':
main()


## Solution Notebook¶

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