题目：

题解：

class Solution:def addStrings(self, num1: str, num2: str) -> str:res = ""i, j, carry = len(num1) - 1, len(num2) - 1, 0while i >= 0 or j >= 0:n1 = int(num1[i]) if i >= 0 else 0n2 = int(num2[j]) if j >= 0 else 0tmp = n1 + n2 + carrycarry = tmp // 10res = str(tmp % 10) + resi, j = i - 1, j - 1return "1" + res if carry else res