题解 | 合法IP

论"0"开头的杀伤力

import sys

def check_ip_str(s):
    if len(s) != 4:
        return False
    for each in s:
        try:
            if "+" in each:
                return False
            if not 0 <= int(each) <= 255:
                return False
            if each.startswith("0") and int(each) != 0:
                return False
        except Exception:
            return False
    return True

for line in sys.stdin:
    if "." not in line:
        print("NO")
        continue
    ip_str = line.split(".")
    print("YES" if check_ip_str(ip_str) else "NO")