Regular Expression Match

class Solution:
    # @param A : string
    # @param B : string
    # @return an integer

    def checkMatch(self, A, B, a, b):


        # if a <= 0 or b <= 0:
        #     self.dp[a][b] = 1 if a == 0 and b == 0 else 0
        #     return self.dp[a][b]
        if a == 0 and b == 0:
            return 1 if A[a] == B[b] or B[b] == "*" or B[b] == "?" else 0

        if a == -1 and b == -1:
            return 1
        elif a == -1 or b == -1:
            return 0

        if self.dp[a][b] != -1:
            return self.dp[a][b]

        if A[a] == B[b] or B[b] == "?":
            self.dp[a][b] = self.checkMatch(A, B, a-1, b-1)
            return self.dp[a][b]

        elif B[b] == "*":
            if b == 0:
                return 1
            ans = self.checkMatch(A, B, a-1, b-1) or self.checkMatch(A, B, a-1, b)
            self.dp[a][b] = ans

            return self.dp[a][b]

        elif A[a] != B[b]:
            self.dp[a][b] = 0
            return 0

    def isMatch(self, A, p):

        pattern = [p[0]]
        for x in range(1, len(p)):
            if p[x-1] == p[x] == "*":
                continue
            else:
                pattern.append(p[x])
        pattern = "".join(pattern)

        self.dp = [[-1]*len(pattern)]*len(A)


        return self.checkMatch(A, pattern, len(A)-1, len(pattern)-1)