<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:

    vector<vector<string>> getIP(string s, int nums, string prefix){

    vector<vector<string>>output;

    // if(prefix.size())
    if(s.size() > nums * 3){
        return output;
    }

    if(s.size() < nums){
        return output;
    }

    if(nums == 1 && prefix.size() + s.size() <=3){
        output.push_back({s});
        return output;
    }

    if(nums==1 && prefix.size() + s.size() >3){
        // vector<string>output;
        // output.push_back(s);
        return output;
    }

    if(s.size()==1 && nums!=1){
        return output;
    }
        // int size = s.size();

    string prefix2 = "";
    vector<vector<string>>a_extend = getIP(s.substr(1, s.size()-1), nums-1, prefix2);
        
    for(int i = 0; i < a_extend.size(); i++){

        if(a_extend[i].size()==nums-1){
            vector<string>a = {prefix+s[0]};
            a.insert(a.end(), a_extend[i].begin(), a_extend[i].end());
            output.push_back(a);
        }
    }

    // a.insert(a.end(), a_extend.begin(), a_extend.end());
        vector<vector<string>>out2 = getIP(s.substr(1, s.size()-1), nums, prefix+s[0]);
        output.insert(output.end(), out2.begin(), out2.end());
        return output;

    }

    vector<string> restoreIpAddresses(string s) {

        string prefix = "";
        vector<vector<string>> output = getIP(s, 4, prefix);

        vector<string>out;

        for(int i = 0; i < output.size(); i++){
            string s = output[i][0];
            if(s.size()>3 || (s.size()>1 && s[0]-'0' == 0)){
                continue;
            } else if(s.size() == 3 && stoi(s)>255){
                continue;
            }
            if(output[i].size()==4){
            bool nota = false;
            for(int j = 1; j < 4; j++){
            
                if(output[i][j].size()>3 || (output[i][j].size()>1 && output[i][j][0]-'0' == 0)){
                // continue;
                nota = true;
                break;
                } else if(output[i][j].size() == 3 && stoi(output[i][j])>255){
                // continue;
                nota = true;
                break;
                }
                s = s + "." + output[i][j];
            }
            if(!nota){

            
            out.push_back(s);
            }
            }
        }

        return out;

    }
};
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