<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 SplitStringsAtDot (string s, vector<string>& res) {
        string str = "";
        for(int i=0;i<s.size();i++) {
            if(s[i] == '.') {
                res.push_back(str);
                str="";
            } else {
                str.push_back(s[i]);
            }
        }
        res.push_back(str);
    }
    bool checkIfSafeSplit (string s) {
        vector<string> splits;
        SplitStringsAtDot (s, splits);
        // for(int i=0;i<splits.size();i++) {
        //     cout<<splits[i]<<" ";
        // }
        // cout<<endl;
        for(int i=0;i<splits.size();i++) {
            if(splits[i].size() > 4 || splits[i].size() == 0) {
                return false;
            } else if(stoi(splits[i]) > 255) {
                return false;
            } else if(splits[i].size() >=2 && splits[i][0] == '0') {
                return false;
            }
        }
        return true;
    }
    void generateAllSplits (string& s, int index, int remaining, vector<string>& res) {
        // cout<<s<<endl;
        // if(s == "255.255.11.135") {
        //     cout<<checkIfSafeSplit(s)<<endl;
        //     cout<<s<<endl;
        // }
        if(remaining > 0 && index > s.size()) {
            // cout<<s<<endl;
            return;
        } else if(remaining == 0 && checkIfSafeSplit(s)) {
            res.push_back(s);
            return;
        } else if(remaining > 0) {
            s.insert(index, ".");
            generateAllSplits(s, index+1, remaining-1, res);
            s.erase(index, 1);
            generateAllSplits(s, index+1, remaining, res);
        }
    }
    vector<string> restoreIpAddresses(string& s) {
        vector<string> res;
        if(s.size() < 4 || s.size() > 12) {
            return res;
        }
        generateAllSplits(s, 1, 3, res); // index of dot, remaining dots
        return res;
    }
};
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