docs(pangram): improve approach's content and links

Author: princemuel

exercises/practice/pangram/.approaches/set-len/content.md

@@ -6,14 +6,13 @@ def is_pangram(sentence):
 ```
 
 - This approach first makes a [set][set] from the [`lower`][lower]cased characters of the `sentence`.
-- The characters in the `set`are then iterated in a [list comprehension][list-comprehension].
-- The characters are filtered by an `if` [`isalpha()`][isalpha] statement, so that only alphabetic characters make it into the list.
-- The function returns whether the [`len()`][len] of the [`list`][list] is `26`.
-  If the number of unique letters in the `set` is equal to the `26` letters in the alphabet, then the function will return `True`.
+- The characters are filtered using a [set comprehension][set-comprehension] with an `if` [`isalpha()`][isalpha] statement, so that only alphabetic characters make it into the set.
+- The function returns whether the [`len()`][len] of the [`set`][set] is `26`.
+  If the number of unique ASCII letters in the `set` is equal to the `26` letters in the ASCII alphabet, then the function will return `True`.
+- This approach is efficient because it uses a set to eliminate duplicates and directly checks the length, which is a constant time operation.
 
 [lower]: https://docs.python.org/3/library/stdtypes.html?#str.lower
 [set]: https://docs.python.org/3/library/stdtypes.html?#set
-[list-comprehension]: https://docs.python.org/3/tutorial/datastructures.html#list-comprehensions
+[set-comprehension]: https://realpython.com/python-set-comprehension/#introducing-set-comprehensions
 [isalpha]: https://docs.python.org/3/library/stdtypes.html?highlight=isalpha#str.isalpha
 [len]: https://docs.python.org/3/library/functions.html?#len
-[list]: https://docs.python.org/3/library/stdtypes.html?#list