<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:

    void checkValidIps(vector<string> s, vector<string> & ips){
        string ip = s[0] + "." + s[1] + "." + s[2] + "." + s[3];
        cout << ip << endl;

        if (s[0].size()>3 || s[1].size()>3 || s[2].size()>3 || s[3].size()>3) return;
        for (int i = 0; i < s.size(); i++){
            //check if withtin 0 to 255 inclusive
            if (!(stoi(s[i]) >= 0) || !(stoi(s[i])<= 255)) return;
            //check if no leading zeros 
            if (s[i].size()> 1 && s[i][0] == '0') return;
        }
        // string ip = s[0] + "." + s[1] + "." + s[2] + "." + s[3];
        ips.push_back(ip);
    }

    vector<string> restoreIpAddresses(string s) {

        int sz = s.size();
        vector<string> ips;
        if (sz < 4) return ips;

        //get all possible ip addresses

        for (int i = 0; i < sz-3; i++){
            for (int j = 1; j < sz-2; j++){
                for (int k = 2; k < sz-1; k++){
                    if (i >= j || j >= k) continue;
                    vector<string> parts;
                    parts.push_back(s.substr(0, i+1));
                    parts.push_back(s.substr(i+1, j-i));
                    parts.push_back(s.substr(j+1, k-j));
                    parts.push_back(s.substr(k+1));
                    checkValidIps(parts, ips);
                }
            }
        }

        return ips;
        
    }
};
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