@@ -6,6 +6,10 @@ 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.
+    
+    Before changes: O(N^2 * avg(string_length)) - each string compared with each other string in double loop.
+    After changes: O(N * logN * avg(string_length))
+    
     """
     if len(strings) <= 1:
         return ""
 
@@ -1,6 +1,10 @@
 def count_letters(s: str) -> int:
     """
     count_letters returns the number of letters which only occur in upper case in the passed string.
+    
+    Before changes: O(N^2) - each letter compared with each other in double loop.
+    After changes: O(N + min(len(set_upper), min(len(set_lower)))
+    
     """
     appeared_upper = set()
     appeared_lower = set()