1. from collections import defaultdict
    4. class Solution:
    5.     def multiply(self, num1: str, num2: str) -> str:
    6.         res = 0
    7.         for i in range(1, len(num1) + 1):
    8.             for j in range(1, len(num2) + 1):
    9.                 res += int(num1[-i]) * int(num2[-j]) * 10 ** (i + j - 2)
    10.         return str(res)
    12.     def multiply(self, num1: str, num2: str) -> str:
    13.         res = 0
    14.         for (i, n1) in enumerate(map(int, num1[::-1])):
    15.             for (j, n2) in enumerate(map(int, num2[::-1])):
    16.                 res += n1 * n2 * 10 ** (i + j)
    17.         return str(res)
    19.     def multiply(self, num1: str, num2: str) -> str:
    20.         tmp = defaultdict(lambda: 0)
    21.         for (i, n1) in enumerate(map(int, num1[::-1])):
    22.             for (j, n2) in enumerate(map(int, num2[::-1])):
    23.                 tmp[i + j] += n1 * n2
    24.         return str(sum(num * 10 ** k for k, num in tmp.items()))
    27. if __name__ == '__main__':
    28.     print(Solution().multiply("2", "3"))
    29.     print(Solution().multiply("123", "456"))