From 030a26244f48137cf6e43fd79cb7b83650e2a4ff Mon Sep 17 00:00:00 2001 From: Gabriel Date: Tue, 13 Jan 2026 15:34:10 +0000 Subject: [PATCH] This is the implementation of improve_with_precomputing --- .../common_prefix/common_prefix.py | 34 ++++++++++++------- .../count_letters/count_letters.py | 6 +++- 2 files changed, 26 insertions(+), 14 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..4ed9977 100644 --- a/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py +++ b/Sprint-2/improve_with_precomputing/common_prefix/common_prefix.py @@ -7,18 +7,26 @@ 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 not strings or len(strings) == 1: + return "" + 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 + + # Precompute: Build a dictionary of prefixes to their count + # For each string, generate all its prefixes and count occurrences + prefix_count = {} + + for string in strings: + seen_prefixes = set() # Avoid counting same prefix twice from same string + for i in range(len(string) + 1): + prefix = string[:i] + if prefix not in seen_prefixes: + prefix_count[prefix] = prefix_count.get(prefix, 0) + 1 + seen_prefixes.add(prefix) + + # Find the longest prefix that appears in at least 2 strings + for prefix, count in prefix_count.items(): + if count >= 2 and len(prefix) > len(longest): + longest = prefix + 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] 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..7fe77c2 100644 --- a/Sprint-2/improve_with_precomputing/count_letters/count_letters.py +++ b/Sprint-2/improve_with_precomputing/count_letters/count_letters.py @@ -2,10 +2,14 @@ def count_letters(s: str) -> int: """ count_letters returns the number of letters which only occur in upper case in the passed string. """ + # Precompute: create set of all lowercase letters in the string (O(n)) + lowercase_letters = set(c for c in s if c.islower()) + + # Now just count uppercase letters that don't have a lowercase version only_upper = set() for letter in s: if is_upper_case(letter): - if letter.lower() not in s: + if letter.lower() not in lowercase_letters: only_upper.add(letter) return len(only_upper)