<p>A <strong>valid IP address</strong> consists of exactly four integers separated by single dots. Each integer is between <code>0</code> and <code>255</code> (<strong>inclusive</strong>) and cannot have leading zeros.</p>

<ul>
	<li>For example, <code>&quot;0.1.2.201&quot;</code> and <code>&quot;192.168.1.1&quot;</code> are <strong>valid</strong> IP addresses, but <code>&quot;0.011.255.245&quot;</code>, <code>&quot;192.168.1.312&quot;</code> and <code>&quot;192.168@1.1&quot;</code> are <strong>invalid</strong> IP addresses.</li>
</ul>

<p>Given a string <code>s</code> containing only digits, return <em>all possible valid IP addresses that can be formed by inserting dots into </em><code>s</code>. You are <strong>not</strong> allowed to reorder or remove any digits in <code>s</code>. You may return the valid IP addresses in <strong>any</strong> order.</p>

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

<pre>
<strong>Input:</strong> s = &quot;25525511135&quot;
<strong>Output:</strong> [&quot;255.255.11.135&quot;,&quot;255.255.111.35&quot;]
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;0000&quot;
<strong>Output:</strong> [&quot;0.0.0.0&quot;]
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;101023&quot;
<strong>Output:</strong> [&quot;1.0.10.23&quot;,&quot;1.0.102.3&quot;,&quot;10.1.0.23&quot;,&quot;10.10.2.3&quot;,&quot;101.0.2.3&quot;]
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 20</code></li>
	<li><code>s</code> consists of digits only.</li>
</ul>

class Solution {
public:
    bool checkLeadingZeroes(string &IP) {
        return (IP.length() > 1 && IP[0] == '0');
    }

    void Restore(string &s, int i, int numPartitions, string &currIP, vector<string> &IP) {
        if (i == s.length()) {
            if (numPartitions != 4) return;
            IP.push_back(currIP.substr(1)); 
            return;
        }

        for (int j = i; j <= min(i + 3, (int)s.length() - 1); j++) {
            string temp = currIP;
            string currPart = s.substr(i, j - i + 1);
            if (checkLeadingZeroes(currPart) || stoi(currPart) > 255) continue;
            currIP += ('.' + currPart);
            Restore(s, j + 1, numPartitions + 1, currIP, IP);
            currIP = temp;
        }
        return;
    }

    vector<string> restoreIpAddresses(string s) {
        string currIP = "";
        vector<string> IP;
        Restore(s, 0, 0, currIP, IP);
        return IP;
    }
};
14993