题解 | #合法IP# 硬编码

while 1:
    try:
        ip = input()
        ip = ip.split('.')
        if len(ip) != 4 :
            print('NO')
            continue
        
        flag = 0
        for i in ip:
            if  i == '':
                flag = 1
                break 
            else:
                if (i[0]  == '0' and i.__len__() > 1) or (i[0]  == '+' and i.__len__() > 1) or (i[0]  == '-' and i.__len__() > 1):
                    flag = 1
                    break
        if flag:
            print('NO')
            continue
        try:
            
            ip = list(map(lambda x: int(x),ip))
        except :
            print('NO')
            continue
        
        for i in ip:
            if i <= 255:
                pass
            else:
                flag = 1
                break
        if flag:
            print('NO')
            continue 
        print('YES')
    except:
        break