Seawolf 发表于 2020-9-25 02:55:01

Leetcode 10. Regular Expression Matching

Given an input string (s) and a pattern (p), implement regular expression matching with support for '.' and '*'.

'.' Matches any single character.
'*' Matches zero or more of the preceding element.
The matching should cover the entire input string (not partial).

Note:

s could be empty and contains only lowercase letters a-z.
p could be empty and contains only lowercase letters a-z, and characters like . or *.
Example 1:

Input:
s = "aa"
p = "a"
Output: false
Explanation: "a" does not match the entire string "aa".
Example 2:

Input:
s = "aa"
p = "a*"
Output: true
Explanation: '*' means zero or more of the preceding element, 'a'. Therefore, by repeating 'a' once, it becomes "aa".
Example 3:

Input:
s = "ab"
p = ".*"
Output: true
Explanation: ".*" means "zero or more (*) of any character (.)".
Example 4:

Input:
s = "aab"
p = "c*a*b"
Output: true
Explanation: c can be repeated 0 times, a can be repeated 1 time. Therefore, it matches "aab".
Example 5:

Input:
s = "mississippi"
p = "mis*is*p*."
Output: false

class Solution:
    def isMatch(self, s: str, p: str) -> bool:
      # X X X X X
      # X X X *
      m = len(s)
      n = len(p)
      dp = [ for _ in range(m + 1)]
      
      s = '#' + s
      p = '#' + p
      
      dp = True
      for j in range(2, n + 1):
            dp = (p == '*' and dp)
      
      for i in range(1, m + 1):
            for j in range(1, n + 1):
                if p.isalpha():
                  dp = (s == p and dp)
                  
                elif p == '.':
                  dp = dp
               
                elif p == '*':
                  dp = ((s == p or p == '.') and dp) or dp
      
      return dp
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