From 5c5e63d08d8436d2b3b862eb9e2b4e565573e3eb Mon Sep 17 00:00:00 2001 From: JanefrancessC Date: Wed, 1 Jul 2026 16:40:54 +0100 Subject: [PATCH 1/2] feat: optimise code with precomputing --- .../common_prefix/common_prefix.py | 16 +++++++++++----- .../count_letters/count_letters.py | 10 ++++------ 2 files changed, 15 insertions(+), 11 deletions(-) diff --git a/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py b/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py index f4839e7..7d8b318 100644 --- a/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py +++ b/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py @@ -7,12 +7,18 @@ def find_longest_common_prefix(strings: List[str]): 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. """ + + if len(strings) < 2: + return "" + + 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 i in range(len(strings) - 1): + common = find_common_prefix(strings[i], strings[i + 1]) + if len(common) > len(longest): + longest = common return longest diff --git a/Sprint-2/improve_with_precomputing/count_letters/count_letters.py b/Sprint-2/improve_with_precomputing/count_letters/count_letters.py index 62c3ec0..d8030a3 100644 --- a/Sprint-2/improve_with_precomputing/count_letters/count_letters.py +++ b/Sprint-2/improve_with_precomputing/count_letters/count_letters.py @@ -2,13 +2,11 @@ def count_letters(s: str) -> int: """ count_letters returns the number of letters which only occur in upper case in the passed string. """ + letters = set(s) only_upper = set() + for letter in s: - if is_upper_case(letter): - if letter.lower() not in s: + if letter.isupper(): + if letter.lower() not in letters: only_upper.add(letter) return len(only_upper) - - -def is_upper_case(letter: str) -> bool: - return letter == letter.upper() From 5e73ed4b81059d9445224d3ab83147725bf0934c Mon Sep 17 00:00:00 2001 From: JanefrancessC Date: Mon, 6 Jul 2026 17:01:16 +0100 Subject: [PATCH 2/2] Include comments to explain the improved complexity against the original code --- .../common_prefix/common_prefix.py | 6 ++++++ .../count_letters/count_letters.py | 4 ++++ 2 files changed, 10 insertions(+) diff --git a/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py b/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py index 7d8b318..0a6e883 100644 --- a/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py +++ b/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py @@ -11,6 +11,12 @@ def find_longest_common_prefix(strings: List[str]): if len(strings) < 2: return "" + # Sorting first (O(n log n * k)) means the longest common prefix between + # ANY two strings in the list is guaranteed to be between two ADJACENT + # strings after sorting. This lets us check only n-1 adjacent pairs + # instead of comparing every pair (O(n^2 * k) in the original version), + # reducing the overall complexity to O(n log n * k). + strings = sorted(strings) longest = "" diff --git a/Sprint-2/improve_with_precomputing/count_letters/count_letters.py b/Sprint-2/improve_with_precomputing/count_letters/count_letters.py index d8030a3..6b2a621 100644 --- a/Sprint-2/improve_with_precomputing/count_letters/count_letters.py +++ b/Sprint-2/improve_with_precomputing/count_letters/count_letters.py @@ -2,6 +2,10 @@ def count_letters(s: str) -> int: """ count_letters returns the number of letters which only occur in upper case in the passed string. """ + # Precompute a set of all characters in s: O(n) once. + # This turns the `letter.lower() not in s` check (O(n) linear scan, + # making the whole function O(n^2)) into an O(1) set lookup, + # bringing the overall complexity down to O(n). letters = set(s) only_upper = set()