LeetCode Challenge — 6/16 Validate IP Address

Write a function to check whether an 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.,;

Besides, leading zeros in the IPv4 is invalid. For example, the address is invalid.

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 is a valid 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 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, is an invalid IPv6 address.

Besides, extra leading zeros in the IPv6 is also invalid. For example, the address is invalid.

Note: You may assume there is no extra space or 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.`

IPv4 :

1. 分隔用"."
2. 第一個字元不可為"0"，只有一個0除外
3. 有四組值
4. 數字在0~255之間

IPv6 :

1. 分隔用":"
2. 8組16進位制
3. 每組字元數量不可>4
4. 不可空字串

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