Validate IP Address
<p>Given a string <code>queryIP</code>, return <code>&quot;IPv4&quot;</code> if IP is a valid IPv4 address, <code>&quot;IPv6&quot;</code> if IP is a valid IPv6 address or <code>&quot;Neither&quot;</code> if IP is not a correct IP of any type.</p>

<p><strong>A valid IPv4</strong> address is an IP in the form <code>&quot;x<sub>1</sub>.x<sub>2</sub>.x<sub>3</sub>.x<sub>4</sub>&quot;</code> where <code>0 &lt;= x<sub>i</sub> &lt;= 255</code> and <code>x<sub>i</sub></code> <strong>cannot contain</strong> leading zeros. For example, <code>&quot;192.168.1.1&quot;</code> and <code>&quot;192.168.1.0&quot;</code> are valid IPv4 addresses while <code>&quot;192.168.01.1&quot;</code>, <code>&quot;192.168.1.00&quot;</code>, and <code>&quot;192.168@1.1&quot;</code> are invalid IPv4 addresses.</p>

<p><strong>A valid IPv6</strong> address is an IP in the form <code>&quot;x<sub>1</sub>:x<sub>2</sub>:x<sub>3</sub>:x<sub>4</sub>:x<sub>5</sub>:x<sub>6</sub>:x<sub>7</sub>:x<sub>8</sub>&quot;</code> where:</p>

<ul>
	<li><code>1 &lt;= x<sub>i</sub>.length &lt;= 4</code></li>
	<li><code>x<sub>i</sub></code> is a <strong>hexadecimal string</strong> which may contain digits, lowercase English letter (<code>&#39;a&#39;</code> to <code>&#39;f&#39;</code>) and upper-case English letters (<code>&#39;A&#39;</code> to <code>&#39;F&#39;</code>).</li>
	<li>Leading zeros are allowed in <code>x<sub>i</sub></code>.</li>
</ul>

<p>For example, &quot;<code>2001:0db8:85a3:0000:0000:8a2e:0370:7334&quot;</code> and &quot;<code>2001:db8:85a3:0:0:8A2E:0370:7334&quot;</code> are valid IPv6 addresses, while &quot;<code>2001:0db8:85a3::8A2E:037j:7334&quot;</code> and &quot;<code>02001:0db8:85a3:0000:0000:8a2e:0370:7334&quot;</code> are invalid IPv6 addresses.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> queryIP = &quot;172.16.254.1&quot;
<strong>Output:</strong> &quot;IPv4&quot;
<strong>Explanation:</strong> This is a valid IPv4 address, return &quot;IPv4&quot;.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> queryIP = &quot;2001:0db8:85a3:0:0:8A2E:0370:7334&quot;
<strong>Output:</strong> &quot;IPv6&quot;
<strong>Explanation:</strong> This is a valid IPv6 address, return &quot;IPv6&quot;.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> queryIP = &quot;256.256.256.256&quot;
<strong>Output:</strong> &quot;Neither&quot;
<strong>Explanation:</strong> This is neither a IPv4 address nor a IPv6 address.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>queryIP</code> consists only of English letters, digits and the characters <code>&#39;.&#39;</code> and <code>&#39;:&#39;</code>.</li>
</ul>
String
func validIPAddress(queryIP string) string {
	if isIPv4(queryIP) {
		return "IPv4"
	}
	if isIPv6(queryIP) {
		return "IPv6"
	}
	return "Neither"
}

func isIPv4(s string) bool {
	if strings.HasSuffix(s, ".") {
		return false
	}
	ss := strings.Split(s, ".")
	if len(ss) != 4 {
		return false
	}
	for _, t := range ss {
		if len(t) == 0 || (len(t) > 1 && t[0] == '0') {
			return false
		}
		x := convert(t)
		if x < 0 || x > 255 {
			return false
		}
	}
	return true
}

func isIPv6(s string) bool {
	if strings.HasSuffix(s, ":") {
		return false
	}
	ss := strings.Split(s, ":")
	if len(ss) != 8 {
		return false
	}
	for _, t := range ss {
		if len(t) < 1 || len(t) > 4 {
			return false
		}
		for _, c := range t {
			if !unicode.IsDigit(c) && !strings.ContainsRune("0123456789abcdefABCDEF", c) {
				return false
			}
		}
	}
	return true
}

func convert(s string) int {
	x := 0
	for _, c := range s {
		if !unicode.IsDigit(c) {
			return -1
		}
		x = x*10 + int(c-'0')
		if x > 255 {
			return x
		}
	}
	return x
}