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

Challenge Notebook

Problem: Given sorted arrays A, B, merge B into A in sorted order.

Constraints

  • Does A have enough space for B?
    • Yes
  • Can the inputs have duplicate array items?
    • Yes
  • Can we assume the inputs are valid?
    • No
  • Does the inputs also include the actual size of A and B?
    • Yes
  • Can we assume this fits memory?
    • Yes

Test Cases

  • A or B is None -> Exception
  • index of last A or B < 0 -> Exception
  • A or B is empty
  • General case
    • A = [1, 3, 5, 7, 9, None, None, None]
    • B = [4, 5, 6]
    • A = [1, 3, 4, 5, 5, 6, 7, 9]

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 Array(object):

    def merge_into(self, source, dest, source_end_index, dest_end_index):
        # TODO: Implement me
        pass

Unit Test

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

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


class TestArray(unittest.TestCase):

    def test_merge_into(self):
        array = Array()
        self.assertRaises(TypeError, array.merge_into, None, None, None, None)
        self.assertRaises(ValueError, array.merge_into, [1], [2], -1, -1)
        a = [1, 2, 3]
        self.assertEqual(array.merge_into(a, [], len(a), 0), [1, 2, 3])
        a = [1, 2, 3]
        self.assertEqual(array.merge_into(a, [], len(a), 0), [1, 2, 3])
        a = [1,  3,  5,  7,  9,  None,  None,  None]
        b = [4,  5,  6]
        expected = [1, 3, 4, 5, 5, 6, 7, 9]
        self.assertEqual(array.merge_into(a, b, 5, len(b)), expected)
        print('Success: test_merge_into')


def main():
    test = TestArray()
    test.test_merge_into()


if __name__ == '__main__':
    main()

Solution Notebook

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