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105 lines
2.7 KiB
Python
105 lines
2.7 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 ^ (m + n)), where m is the length of text and n is the length of pattern.
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Space complexity: Recursion depth is O(m + n).
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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 text and not pattern:
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return True
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if text and not pattern:
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return False
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if not text and pattern and pattern[-1] != "*":
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return False
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if not text and pattern and pattern[-1] == "*":
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return 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(m * n), where m is the length of text and n is the length of pattern.
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Space complexity: O(m * n).
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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 i in range(1, m + 1):
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dp[i][0] = False
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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] == "." or pattern[j - 1] == 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] or ((pattern[j - 2] == "." or pattern[j - 2] == text[i - 1]) and 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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