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

# Challenge Notebook¶

## Constraints¶

• Is there exactly one solution?
• Yes
• Is there always a solution?
• Yes
• Is the array an array of ints?
• Yes
• Is the array sorted? No
• Are negative values possible?
• Yes
• Can we assume the inputs are valid?
• No
• Can we assume this fits memory?
• Yes

## Test Cases¶

• None input -> TypeError
• [] -> ValueError
• [1, 3, 2, -7, 5], 7 -> [2, 4]

## 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 two_sum(self, nums, val):
# TODO: Implement me
pass


## Unit Test¶

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

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

class TestTwoSum(unittest.TestCase):

def test_two_sum(self):
solution = Solution()
self.assertRaises(TypeError, solution.two_sum, None, None)
self.assertRaises(ValueError, solution.two_sum, [], 0)
target = 7
nums = [1, 3, 2, -7, 5]
expected = [2, 4]
self.assertEqual(solution.two_sum(nums, target), expected)
print('Success: test_two_sum')

def main():
test = TestTwoSum()
test.test_two_sum()

if __name__ == '__main__':
main()


## Solution Notebook¶

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