题解 | #判断两个IP是否属于同一子网#

```def checkip(lst):
    for i in lst:
        if int(i) < 0 or int(i) > 255:
            return False
    return True
def checkmask(lst):
    i = changebin(lst)
    if i[0] != '11111111' or i[-1] != '00000000':
        return False
    else:
        return checkip(lst)
def changebin(lst):
    res = []
    for i in lst:
        res.append(bin(int(i))[2:].rjust(8, '0'))
    return res
def checksame(ip1_bin, ip2_bin, mask_bin):
    count = 0
    for i in range(4):
        a = int(ip1_bin[i], 2) & int(mask_bin[i], 2)
        b = int(ip2_bin[i], 2) & int(mask_bin[i], 2)
        if a == b:
            count += 1
    if count == 4:
        return True
    else:
        return False
    
while True:
    try:
        mask = input().split('.')
        ip1 = input().split('.')
        ip2 = input().split('.')
        ip1_bin = []
        ip2_bin = []
        mask_bin = []
        if checkmask(mask) and checkip(ip1) and checkip(ip2):
            ip1_bin = changebin(ip1)
            ip2_bin = changebin(ip2)
            mask_bin = changebin(mask)
            if checksame(ip1_bin, ip2_bin, mask_bin):
                print('0')
            else:
                print('2')
        else:
             print('1')
    except:
        break