<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:
    string curr;
    vector<string> ans;
    string st;
    vector<string> split(string s, char ch){
        vector<string> splitted;
        string turn;
        stringstream ss (s);
        while(getline(ss, turn, ch)){
            splitted.push_back(turn);
        }
        // for(auto it: splitted){
        //     cout<<it<<" ";
        // }
        
        return splitted;
    }
    bool valid(string s){
        vector<string> fs = split(s, '.');
        

        if(fs.size()<4)return false;
        for(auto v: fs){
            long long x  = stoll(v);
            if(v.size()>1 && v[0]=='0')return false;
            if(x>255)return false;
            
        }
        return true;
    }
    void rec(int level, int k){
        if(k>3)return;
        if(level == st.size()){

            if(k==3 && valid(curr)){
                // cout<<"it is valid"<<curr<<endl;
                ans.push_back(curr);
            }
            return ;
        }

        curr.push_back(st[level]);
        rec(level+1, k);
        curr.pop_back();

        curr.push_back(st[level]);
        curr.push_back('.');
        rec(level+1, k+1);
        curr.pop_back();
        curr.pop_back();

        return;
    }
    vector<string> restoreIpAddresses(string s) {
        st = s;
        rec(0, 0);
        return ans;
    }
};
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