<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>

class Solution {
public:
    // validv4()
        // ...
        // .00.
        // .10
        // 00.12.22.34
    // validv6()
    string validV4(string &address){
        int num = -1 , cntPeriod = 0;
        for(int i = 0;i<address.size();i++) {
            if(address[i] != '.'){
                if(address[i]>='0' && address[i] <= '9'){
                    if(num < 0) num = 0;
                    num = num*10 + (address[i]-'0');
                    if(num < 0 || num>255) {
                        return "Neither";
                    }

                    // Handle Leading Zeros
                    if(i!=0 && address[i] == '0' && address[i-1] == '.'){
                        if(i!=(address.size()-1) && address[i+1] != '.') return "Neither";
                    }
                    if(i==0 && address[i] == '0'){
                        if(i!=(address.size()-1) && address[i+1] != '.') return "Neither";
                    }
                } else {
                    return "Neither";
                }
            } else {
                cntPeriod++;
                if(num < 0 || num>255) return "Neither";
                num = -1;
            }
        }
        // For the last number
        if(num < 0 || num>255) return "Neither";

        return cntPeriod == 3 ? "IPv4" : "Neither";
    }
    string validV6(string &address){
        int numLength = 0 , cntColon = 0;
        for(int i = 0;i<address.size();i++) {
            if(address[i] != ':'){
                if((address[i]>='0' && address[i] <= '9') || (address[i]>='A' && address[i] <= 'F') || (address[i]>='a' && address[i]<='f')){
                    numLength++;
                    if(numLength < 1 || numLength > 4) return "Neither";
                } else {
                    return "Neither";
                }
            } else {
                cntColon++;
                if(numLength < 1 || numLength > 4) return "Neither";
                numLength = 0;
            }
        }
        // For the last number
        if(numLength < 1 || numLength>4) return "Neither";

        return cntColon == 7 ? "IPv6" : "Neither";
    }
    string validIPAddress(string queryIP) {
        for(int i = 0;i<queryIP.size();i++) {
            if(queryIP[i] == '.') {
                return validV4(queryIP);
            } else if(queryIP[i] == ':'){
                return validV6(queryIP);
            }
        }
        return "Neither";
    }
};
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