Add optimization details

Author: PratiAmalden

Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py

@@ -6,6 +6,13 @@ def find_longest_common_prefix(strings: List[str]):
     find_longest_common_prefix returns the longest string common at the start of any two strings in the passed list.
 
     In the event that an empty list, a list containing one string, or a list of strings with no common prefixes is passed, the empty string will be returned.
+
+    Optimisation:
+    - Sort the list first
+    - Similar strings end up next to each other
+    - Compare neighbours only instead of all pairs
+
+    Complexity: O(n^2) -> O(n log n)
     """
 
     if not strings or len(strings) < 2:

Sprint-2/improve_with_precomputing/count_letters/count_letters.py

@@ -1,6 +1,12 @@
 def count_letters(s: str) -> int:
     """
     count_letters returns the number of letters which only occur in upper case in the passed string.
+
+    Optimisation:
+    - Convert string to set
+    - Avoid checking the whole string every time
+
+    Complicity: O(n^2) -> O(n)
     """
     chars = set(s)  # precompute all characters once