题解 | 判断两个IP是否属于同一子网

import sys

# 输入处理：'__.__.__.__' --> [__,__,__,__] >> 判断ip是否合法
# 输入处理：'__.__.__.__' -->  '____' 32位二进制字符串 >> 判断子网掩码是否合法 and 进行AND运算，判断是否在同一子网

n,x,y = sys.stdin.read().split()

def ten_two(s):
    """10进制的'__.__.__.__'转换为长度为32的二进制字符串"""
    lst_s = list(map(int,s.split('.')))
    lst_s_2 = []
    for ss in lst_s:
        ss_2 = bin(ss)[2:]
        if len(ss_2) < 8:
            ss_2 = '0' * (8 - len(ss_2)) + ss_2
        lst_s_2.append(ss_2)
    return ''.join(lst_s_2)

def islegal(s):
    """判断是否0 <= __ <= 255,参数s是十进制的'__.__.__.__'字符串"""
    lst_s = list(map(int,s.split('.')))
    for ss in lst_s:
        if 0 <= ss <= 255:
            pass
        else:
            return False
    return True

def net_islegal(s):
    """判断子网掩码是否合法"""
    if islegal(s):
        s_2 = ten_two(s)
        i = 0 
        while s_2[i] == '1':
            i += 1
        if '1' in s_2[i+1:]:
            return False
        return True
    else:
        return False

if net_islegal(n) and islegal(x) and islegal(y):
    n_2 = ten_two(n)
    x_2 = ten_two(x)
    y_2 = ten_two(y)
    x_2_and = ''.join('1' if n_2[i] == '1' and x_2[i] == '1' else '0' for i in range(32))
    y_2_and = ''.join('1' if n_2[i] == '1' and y_2[i] == '1' else '0' for i in range(32))
    if x_2_and == y_2_and:
        print('0')
    else:
        print('2')
else:
    print('1')

出现的错误：

1.子网掩码需要两步验证：

1）0～255

2）'1' * x + '0' * (32-x)

2.ip验证只需要2）

3.字符串切片的结果仍是字符串，写判断时等号右边易写成数值，导致所有判断全部为False