From 47a44abe23870ca0f7c8062601278645039b1c70 Mon Sep 17 00:00:00 2001 From: Alfredo Hernandez Baeza Date: Sat, 10 May 2025 07:57:43 -0400 Subject: [PATCH] Improve longest_common_substring.py (#12705) * Update longest_common_substring.py - Combined the ans_index and ans_length into a single tuple to track the best match (position + length) more cleanly. - Early exit for empty strings. * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Update longest_common_substring.py * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Maxim Smolskiy --- dynamic_programming/longest_common_substring.py | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/dynamic_programming/longest_common_substring.py b/dynamic_programming/longest_common_substring.py index ea5233eb2..3ba83f3d9 100644 --- a/dynamic_programming/longest_common_substring.py +++ b/dynamic_programming/longest_common_substring.py @@ -43,22 +43,25 @@ def longest_common_substring(text1: str, text2: str) -> str: if not (isinstance(text1, str) and isinstance(text2, str)): raise ValueError("longest_common_substring() takes two strings for inputs") + if not text1 or not text2: + return "" + text1_length = len(text1) text2_length = len(text2) dp = [[0] * (text2_length + 1) for _ in range(text1_length + 1)] - ans_index = 0 - ans_length = 0 + end_pos = 0 + max_length = 0 for i in range(1, text1_length + 1): for j in range(1, text2_length + 1): if text1[i - 1] == text2[j - 1]: dp[i][j] = 1 + dp[i - 1][j - 1] - if dp[i][j] > ans_length: - ans_index = i - ans_length = dp[i][j] + if dp[i][j] > max_length: + end_pos = i + max_length = dp[i][j] - return text1[ans_index - ans_length : ans_index] + return text1[end_pos - max_length : end_pos] if __name__ == "__main__":