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