题目描述：

LeetCode 468. Validate IP Address

In this problem, your job to write a function to check whether a input string is a valid IPv4 address or IPv6 address or neither.

IPv4 addresses are canonically represented in dot-decimal notation, which consists of four decimal numbers, each ranging from 0 to 255, separated by dots ("."), e.g.,172.16.254.1;

Besides, you need to keep in mind that leading zeros in the IPv4 is illegal. For example, the address 172.16.254.01 is illegal.

IPv6 addresses are represented as eight groups of four hexadecimal digits, each group representing 16 bits. The groups are separated by colons (":"). For example, the address 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is a legal one. Also, we could omit some leading zeros among four hexadecimal digits and some low-case characters in the address to upper-case ones, so 2001:db8:85a3:0:0:8A2E:0370:7334 is also a valid IPv6 address(Omit leading zeros and using upper cases).

However, we don't replace a consecutive group of zero value with a single empty group using two consecutive colons (::) to pursue simplicity. For example, 2001:0db8:85a3::8A2E:0370:7334 is an invalid IPv6 address.

Besides, you need to keep in mind that extra leading zeros in the IPv6 is also illegal. For example, the address 02001:0db8:85a3:0000:0000:8a2e:0370:7334 is also illegal.

Note: You could assume there is no extra space in the test cases and there may some special characters in the input string.

Example 1:

Input: "172.16.254.1"

Output: "IPv4"

Explanation: This is a valid IPv4 address, return "IPv4".

Example 2:

Input: "2001:0db8:85a3:0:0:8A2E:0370:7334"

Output: "IPv6"

Explanation: This is a valid IPv6 address, return "IPv6".

Example 3:

Input: "256.256.256.256"

Output: "Neither"

Explanation: This is neither a IPv4 address nor a IPv6 address.

题目大意：

编写函数，判断给定的IP地址是否为有效的IPv4地址或者Ipv6地址。

Ipv4地址为4个以点分隔的数字，范围0到255，例如172.16.254.1。

此外，Ipv4不允许出现前缀0。例如地址172.16.254.01是无效的。

Ipv6地址为8个以冒号分隔的16进制数字，例如2001:0db8:85a3:0000:0000:8a2e:0370:7334。允许出现前缀0，并且小写字母和大写字母可以同时出现，所以2001:db8:85a3:0:0:8A2E:0370:7334也是有效的IPv6地址。

然而，不允许出现两个连续的冒号。例如2001:0db8:85a3::8A2E:0370:7334是无效的。

此外，IPv6地址中每一个数字的长度不应大于4位，例如02001:0db8:85a3:0000:0000:8a2e:0370:7334是无效的。

注意：你可以假设测试用例中没有额外的空白字符，但是可能会包含一些特殊字符。

解题思路：

字符串模拟题，根据规则逐一验证即可

Python代码：

class Solution(object):
    def validIPAddress(self, IP):
        """
        :type IP: str
        :rtype: str
        """
        if self.validIPV4(IP):
            return 'IPv4'
        if self.validIPV6(IP):
            return 'IPv6'
        return 'Neither'

    def validIPV4(self, IP):
        parts = IP.split('.')
        if len(parts) != 4: return False
        for part in parts:
            if not part: return False
            if not part.isdigit(): return False
            if part[0] == '0' and len(part) > 1: return False
            if int(part) > 255: return False
        return True

    def validIPV6(self, IP):
        parts = IP.split(':')
        if len(parts) != 8: return False
        for part in parts:
            if not part: return False
            if len(part) > 4: return False
            if any(c not in string.hexdigits for c in part): return False
        return True

 

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