字符串相加

def solve():
    def addStrings(num1, num2):
        i, j = len(num1)-1, len(num2)-1
        carry = 0
        result = []
        while i >= 0 or j >= 0 or carry:
            n1 = int(num1[i]) if i >= 0 else 0
            n2 = int(num2[j]) if j >= 0 else 0
            total = n1 + n2 + carry
            carry = total // 10
            result.append(str(total % 10))
            i -= 1
            j -= 1
        return ''.join(result[::-1])
    print(addStrings('11', '123'))