Regular Expression Matching Python Solution

lcpy gen -n 10   # by problem number
lcpy gen -s regular_expression_matching   # by problem name

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

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".

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

class Solution:
    # Time: O(m * n)
    # Space: O(m * n)
    def is_match(self, s: str, p: str) -> bool:
        m, n = len(s), len(p)
        dp = [[False] * (n + 1) for _ in range(m + 1)]
        dp[0][0] = True

        for j in range(2, n + 1):
            if p[j - 1] == "*":
                dp[0][j] = dp[0][j - 2]

        for i in range(1, m + 1):
            for j in range(1, n + 1):
                if p[j - 1] == s[i - 1] or p[j - 1] == ".":
                    dp[i][j] = dp[i - 1][j - 1]
                elif p[j - 1] == "*":
                    dp[i][j] = dp[i][j - 2]
                    if p[j - 2] == s[i - 1] or p[j - 2] == ".":
                        dp[i][j] = dp[i][j] or dp[i - 1][j]

        return dp[m][n]