leetcode 43: Multiply Strings

Runtime: 64 ms, faster than 75.88% of Python3 online submissions for Multiply Strings.
难不成这用其他语言很难？？？这个还中级难度。。。应该是有其他独特的方法吧

class Solution:
    def multiply(self, num1, num2):
        """
        :type num1: str
        :type num2: str
        :rtype: str
        """
        num1 = int(num1)
        num2 = int(num2)
        num3 = str(num1 * num2)
        return num3