Python 代码实现:

while True:
    try:
        IP_list = list(input().split('.'))
        if len(IP_list) != 4:
            print('NO')
            continue
        for i in IP_list:
            if not i.isdigit():
                print('NO')
                break
            if int(i) < 0 or int(i) > 255:
                print('NO')
                break
            elif i.startswith('0') and not i.endswith('0'):
                print('NO')
                break
        else:
            print('YES')
    except:
        break