718. maximum length of repeated subarray

class (object):
    def findLength(self, A, B):
        """
        :type A: List[int]
        :type B: List[int]
        :rtype: int
        """
        if len(A)==0 or len(B)==0:
            return 0
        dp = [[0]*len(B) for _ in range(len(A))]
        max_len = 0
        for i in range(len(A)):
            for j in range(len(B)):
                if A[i]==B[j]:
                    if i==0 or j==0:
                        dp[i][j] = 1
                    else:
                        dp[i][j] = dp[i-1][j-1] + 1
                max_len = max(max_len, dp[i][j])
        return max_len