Add clarification on sorted array assumption in comments

The added comments explain why the two-pointer approach works due to the sorted nature of the input array. This provides context for the algorithm and highlights its dependency on the input's precondition.

Author: nicholasadamou

Two Pointers/two_sum_II.py

@@ -3,6 +3,9 @@
 import unittest
 from typing import List
 
+# This approach works because we are told that `nums` is sorted
+# If the array was not sorted, we would have to sort it first, and
+# incur a O(n log n) time complexity.
 
 def two_sum_II(nums: List[int], target: int) -> List[int]:
     n = len(nums)