【lc】415 字符串相加

class Solution:
    def addStrings(self, num1: str, num2: str) -> str:
        num1, num2 = (num1, num2) if len(num1) > len(num2) else (num2, num1)
        r_num1, r_num2 = list(num1)[::-1], list(num2)[::-1]
        res = []
        remains = 0
        for i in range(len(r_num1)):
            if i < len(r_num2):
                tmp_val = int(r_num1[i]) + int(r_num2[i]) + remains
            else:
                tmp_val = int(r_num1[i]) + remains
            res.append(str(tmp_val % 10))
            remains = tmp_val // 10
        if remains > 0:
            res.append(str(remains))
        return ''.join(res[::-1])