feat(arrays): two sum

Author: BrianLusina

algorithms/arrays/two_sum/README.md

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+# Two Sum - Input Array Is Sorted
+
+Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that
+they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <=
+index1 < index2 <= numbers.length.
+
+Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2.
+
+The tests are generated such that there is exactly one solution. You may not use the same element twice.
+
+Your solution must use only constant extra space.
+
+```text
+
+Example 1:
+
+Input: numbers = [2,7,11,15], target = 9
+Output: [1,2]
+Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2].
+```
+
+```text
+Example 2:
+
+Input: numbers = [2,3,4], target = 6
+Output: [1,3]
+Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3].
+```
+
+```text
+Example 3:
+
+Input: numbers = [-1,0], target = -1
+Output: [1,2]
+Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1, index2 = 2. We return [1, 2].
+```
+
+## Related Topics
+
+- Array
+- Two Pointers
+- Binary Search

algorithms/arrays/two_sum/__init__.py

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+from typing import List
+
+
+def two_sum(numbers: List[int], target: int) -> List[int]:
+    m = {}
+
+    for idx, num in enumerate(numbers, start=1):
+        complement = target - num
+
+        if complement in m:
+            return [m[complement], idx]
+        m[num] = idx

algorithms/arrays/two_sum/test_two_sum.py

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+import unittest
+from . import two_sum
+
+
+class TwoSumTestCase(unittest.TestCase):
+    def test_1(self):
+        """numbers = [2,7,11,15], target = 9"""
+        numbers = [2, 7, 11, 15]
+        target = 9
+        expected = [1, 2]
+        actual = two_sum(numbers, target)
+        self.assertEqual(expected, actual)
+
+    def test_2(self):
+        """numbers = [2,3,4], target = 6"""
+        numbers = [2, 3, 4]
+        target = 6
+        expected = [1, 3]
+        actual = two_sum(numbers, target)
+        self.assertEqual(expected, actual)
+
+    def test_3(self):
+        """numbers = [-1,0], target = -1"""
+        numbers = [-1, 0]
+        target = -1
+        expected = [1, 2]
+        actual = two_sum(numbers, target)
+        self.assertEqual(expected, actual)
+
+
+if __name__ == '__main__':
+    unittest.main()