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"""
Regex matching check if a text matches pattern or not.
Pattern:
1. ``.`` Matches any single character.
2. ``*`` Matches zero or more of the preceding element.
More info:
https://medium.com/trick-the-interviwer/regular-expression-matching-9972eb74c03
"""
def recursive_match(text: str, pattern: str) -> bool:
r"""
Recursive matching algorithm.
| Time complexity: O(2^(\|text\| + \|pattern\|))
| Space complexity: Recursion depth is O(\|text\| + \|pattern\|).
:param text: Text to match.
:param pattern: Pattern to match.
:return: ``True`` if `text` matches `pattern`, ``False`` otherwise.
>>> recursive_match('abc', 'a.c')
True
>>> recursive_match('abc', 'af*.c')
True
>>> recursive_match('abc', 'a.c*')
True
>>> recursive_match('abc', 'a.c*d')
False
>>> recursive_match('aa', '.*')
True
"""
if not pattern:
return not text
if not text:
return pattern[-1] == "*" and recursive_match(text, pattern[:-2])
if text[-1] == pattern[-1] or pattern[-1] == ".":
return recursive_match(text[:-1], pattern[:-1])
if pattern[-1] == "*":
return recursive_match(text[:-1], pattern) or recursive_match(
text, pattern[:-2]
)
return False
def dp_match(text: str, pattern: str) -> bool:
r"""
Dynamic programming matching algorithm.
| Time complexity: O(\|text\| * \|pattern\|)
| Space complexity: O(\|text\| * \|pattern\|)
:param text: Text to match.
:param pattern: Pattern to match.
:return: ``True`` if `text` matches `pattern`, ``False`` otherwise.
>>> dp_match('abc', 'a.c')
True
>>> dp_match('abc', 'af*.c')
True
>>> dp_match('abc', 'a.c*')
True
>>> dp_match('abc', 'a.c*d')
False
>>> dp_match('aa', '.*')
True
"""
m = len(text)
n = len(pattern)
dp = [[False for _ in range(n + 1)] for _ in range(m + 1)]
dp[0][0] = True
for j in range(1, n + 1):
dp[0][j] = pattern[j - 1] == "*" and dp[0][j - 2]
for i in range(1, m + 1):
for j in range(1, n + 1):
if pattern[j - 1] in {".", text[i - 1]}:
dp[i][j] = dp[i - 1][j - 1]
elif pattern[j - 1] == "*":
dp[i][j] = dp[i][j - 2]
if pattern[j - 2] in {".", text[i - 1]}:
dp[i][j] |= dp[i - 1][j]
else:
dp[i][j] = False
return dp[m][n]
if __name__ == "__main__":
import doctest
doctest.testmod()