1 class Solution: 2 def addStrings(self, num1: str, num2: str) -> str: 3 ans = "" 4 i,j,carry=len(num1)-1,len(num2)-1,0 5 while i >=0 or j >= 0: 6 s = carry 7 if i >= 0: 8 s += int(num1[i]) 9 i -= 1 10 if j >= 0: 11 s += int(num2[j]) 12 j -= 1 13 carry = s // 10 14 ans += str(s % 10) 15 ans += '1' if carry == 1 else '' 16 return ans[::-1]