使用牛客的debug端点调试监视了ls输出都是正确的,不知道为什么无法accept

class Solution:
    def merge(self , A, m, B, n):
        # write code here
        ls = []
        if A == []:
            return B
        if B == []:
            return A
        i = j = 0
        while i < m and j < n:
            if A[i] <= B[j]:
                ls.append(A[i])
                i+=1
            else:
                ls.append(B[j])
                j+=1
        ls.extend(A[i:m])
        ls.extend(B[j:])
        return ls