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* Add recursive solution to regex_match.py * Add dp solution to regex_match.py * Add link to regex_match.py * Minor edit * Minor change * Minor change * Update dynamic_programming/regex_match.py Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com> * Update dynamic_programming/regex_match.py Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com> * Fix ruff formatting in if statements * Update dynamic_programming/regex_match.py Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com> * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci --------- Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com> Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
98 lines
2.4 KiB
Python
98 lines
2.4 KiB
Python
"""
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Regex matching check if a text matches pattern or not.
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Pattern:
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'.' Matches any single character.
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'*' Matches zero or more of the preceding element.
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More info:
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https://medium.com/trick-the-interviwer/regular-expression-matching-9972eb74c03
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"""
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def recursive_match(text: str, pattern: str) -> bool:
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"""
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Recursive matching algorithm.
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Time complexity: O(2 ^ (|text| + |pattern|))
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Space complexity: Recursion depth is O(|text| + |pattern|).
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:param text: Text to match.
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:param pattern: Pattern to match.
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:return: True if text matches pattern, False otherwise.
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>>> recursive_match('abc', 'a.c')
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True
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>>> recursive_match('abc', 'af*.c')
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True
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>>> recursive_match('abc', 'a.c*')
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True
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>>> recursive_match('abc', 'a.c*d')
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False
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>>> recursive_match('aa', '.*')
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True
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"""
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if not pattern:
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return not text
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if not text:
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return pattern[-1] == "*" and recursive_match(text, pattern[:-2])
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if text[-1] == pattern[-1] or pattern[-1] == ".":
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return recursive_match(text[:-1], pattern[:-1])
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if pattern[-1] == "*":
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return recursive_match(text[:-1], pattern) or recursive_match(
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text, pattern[:-2]
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)
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return False
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def dp_match(text: str, pattern: str) -> bool:
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"""
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Dynamic programming matching algorithm.
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Time complexity: O(|text| * |pattern|)
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Space complexity: O(|text| * |pattern|)
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:param text: Text to match.
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:param pattern: Pattern to match.
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:return: True if text matches pattern, False otherwise.
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>>> dp_match('abc', 'a.c')
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True
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>>> dp_match('abc', 'af*.c')
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True
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>>> dp_match('abc', 'a.c*')
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True
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>>> dp_match('abc', 'a.c*d')
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False
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>>> dp_match('aa', '.*')
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True
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"""
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m = len(text)
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n = len(pattern)
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dp = [[False for _ in range(n + 1)] for _ in range(m + 1)]
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dp[0][0] = True
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for j in range(1, n + 1):
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dp[0][j] = pattern[j - 1] == "*" and dp[0][j - 2]
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for i in range(1, m + 1):
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for j in range(1, n + 1):
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if pattern[j - 1] in {".", text[i - 1]}:
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dp[i][j] = dp[i - 1][j - 1]
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elif pattern[j - 1] == "*":
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dp[i][j] = dp[i][j - 2]
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if pattern[j - 2] in {".", text[i - 1]}:
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dp[i][j] |= dp[i - 1][j]
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else:
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dp[i][j] = False
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return dp[m][n]
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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