数据结构与算法-

def big_num_sum(num1: str, num2: str) -> str:
    """
    边界条件：输入非数值
    测试案例：
    1. 包含有非数值的字符串
    2. 正常大的整数
    """
    assert num1.isdigit() == True
    assert num2.isdigit() == True
    long_num, short_num = (num1, num2) if (len(num1) > len(num2)) else (num2, num1)  # c

    long_num = long_num[::-1] # 倒序
    short_num = short_num[::-1] 

    long_len = len(long_num)  # 字符的长度
    short_len = len(short_num)

    for i in range(long_len - short_len):  # 将较短的数值后面补 0 补到和较长的数一样的长度
        short_num += "0"
    result = ""  # 用来保存结果
    flag = 0  # 进位标志位
    for i in range(long_len):
        temp = int(long_num[i]) + int(short_num[i]) + flag
        if temp >= 10:
            result += str(temp-10)
            flag = 1 # 
        else:
            result += str(temp)
            flag = 0
    return int(result[::-1])

if __name__ == "__main__":
    assert (big_num_sum("1234533333133333336", "88888888888888") == 1234533333133333336+88888888888888) == True
    assert (big_num_sum("0", "1") == 0+1) == True
    assert (big_num_sum("0", "d"))  # 非数值输入会报错，用来测试边界条件