From c10a129684a14bb9a5087e150ccfc44f41eba6ec Mon Sep 17 00:00:00 2001 From: pratiamalden Date: Fri, 12 Dec 2025 22:58:53 +0000 Subject: [PATCH 1/3] find_longest_common_prefix precomputing --- .../common_prefix/common_prefix.py | 30 +++++++++++-------- 1 file changed, 17 insertions(+), 13 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..bcdae39 100644 --- a/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py +++ b/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py @@ -1,24 +1,28 @@ from typing import List -def find_longest_common_prefix(strings: List[str]): +def find_longest_common_prefix(strings: List[str]) -> 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. """ + + if not strings or len(strings) < 2: + return "" + + # Precompute sorted strings + 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 - return longest + for i in range(len(sorted_strings) - 1): + s1, s2 = sorted_strings[i], sorted_strings[i + 1] + # Find common prefix between them + prefix_len = 0 + max_len = min(len(s1), len(s2)) + while prefix_len < max_len and s1[prefix_len] == s2[prefix_len]: + prefix_len += 1 + if prefix_len > len(longest): + longest = s1[:prefix_len] -def find_common_prefix(left: str, right: str) -> str: - min_length = min(len(left), len(right)) - for i in range(min_length): - if left[i] != right[i]: - return left[:i] - return left[:min_length] + return longest From 90d768e6fddadd9668da761be0dca935ca5c7443 Mon Sep 17 00:00:00 2001 From: pratiamalden Date: Wed, 25 Feb 2026 23:13:05 +0000 Subject: [PATCH 2/3] Optimize count_letters using precomputed character set for O(n) performance --- .../count_letters/count_letters.py | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) 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..6aee0d9 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. """ - only_upper = set() - for letter in s: - if is_upper_case(letter): - if letter.lower() not in s: - only_upper.add(letter) - return len(only_upper) + chars = set(s) # precompute all characters once + only_upper = set() + for letter in chars: # iterate unique characters only + if letter.isupper() and letter.lower() not in chars: + only_upper.add(letter) -def is_upper_case(letter: str) -> bool: - return letter == letter.upper() + return len(only_upper) \ No newline at end of file From dc097fe04268dccfdef2e837fa9a830437f4f5a4 Mon Sep 17 00:00:00 2001 From: pratiamalden Date: Wed, 25 Feb 2026 23:20:20 +0000 Subject: [PATCH 3/3] Use find_common_prefix helper as suggested --- .../common_prefix/common_prefix.py | 21 +++++++++++-------- 1 file changed, 12 insertions(+), 9 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 bcdae39..7c35053 100644 --- a/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py +++ b/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py @@ -1,7 +1,7 @@ from typing import List -def find_longest_common_prefix(strings: List[str]) -> str: +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. @@ -16,13 +16,16 @@ def find_longest_common_prefix(strings: List[str]) -> str: longest = "" for i in range(len(sorted_strings) - 1): - s1, s2 = sorted_strings[i], sorted_strings[i + 1] - # Find common prefix between them - prefix_len = 0 - max_len = min(len(s1), len(s2)) - while prefix_len < max_len and s1[prefix_len] == s2[prefix_len]: - prefix_len += 1 - if prefix_len > len(longest): - longest = s1[:prefix_len] + common = find_common_prefix(sorted_strings[i], sorted_strings[i + 1]) + if len(common) > len(longest): + longest = common return longest + + +def find_common_prefix(left: str, right: str) -> str: + min_length = min(len(left), len(right)) + for i in range(min_length): + if left[i] != right[i]: + return left[:i] + return left[:min_length]