原题传送门

1. 题目描述

2. Solution

1、思路
把ip全转换为32bit 字符串，模拟与运算。
2、实现

import sys  if sys.platform != linux:     file_in = open(input/HJ39.txt)     sys.stdin = file_in   若IP地址或子网掩码格式非法则输出1，若IP1与IP2属于同一子网络输出0，若IP1与IP2不属于同一子网络输出2。    def is_valid_ip(s):     if .. in s:         return False     for x in list(map(int, s.split(.))):         if x < 0 or x > 255:             return False     return True   def is_valid_mask(mask):     if not is_valid_ip(mask):         return False     mask_bin = ip2bin(mask)     if '0' not in mask_bin or '1' not in mask_bin or '01' in mask_bin:         return False     return True   def int2bin(n):     n_bin = bin(n).replace(0b, )     return f'{0 * (8 - len(n_bin))}{n_bin}'   def ip2bin(s):     nums = list(map(int, s.split(.)))     return .join([int2bin(x) for x in nums])   def solve(ip1, ip2, mask):     if not is_valid_ip(ip1) or not is_valid_ip(ip2) or not is_valid_mask(mask):         print(1)         return     ip1_bin = ip2bin(ip1)     ip2_bin = ip2bin(ip2)     mask_bin = ip2bin(mask)     for i in range(32):         if mask_bin[i] == '0':             continue         if ip1_bin[i] != ip2_bin[i]:             print(2)             return     print(0)   while True:     try:         mask = input().strip()         ip1 = input().strip()         ip2 = input().strip()         solve(ip1, ip2, mask)     except:         break