Optimize common_prefix and count_letters with precomputing

Author: RahwaZeslusHaile

Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py

@@ -2,17 +2,16 @@
 
 
 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.
+  
+    if len(strings) < 2:
+        return ""
 
-    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.
-    """
+    sorted_strings = sorted(strings)
     longest = ""
-    for string_index, string in enumerate(strings):
-        for other_string in strings[string_index+1:]:
-            common = find_common_prefix(string, other_string)
-            if len(common) > len(longest):
-                longest = common
+    for index in range(len(sorted_strings) - 1):
+        common = find_common_prefix(sorted_strings[index], sorted_strings[index + 1])
+        if len(common) > len(longest):
+            longest = common
     return longest
 
 

Sprint-2/improve_with_precomputing/count_letters/count_letters.py

@@ -1,11 +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.
-    """
+   
+    lower_letters = {letter for letter in s if letter.islower()}
     only_upper = set()
     for letter in s:
         if is_upper_case(letter):
-            if letter.lower() not in s:
+            if letter.lower() not in lower_letters:
                 only_upper.add(letter)
     return len(only_upper)