<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<string> sol;
    bool isvalid(string str)
    {
         if(str.length() == 0)
         return false;
         if(stoi(str) > 255)
         return false;

         if(str.length() > 1 && str[0]=='0')
         return false;

         return true;
    }
    void restoreAdd(string s, int n, string s1, int i, int start)
    {
          if(i==5 && s1.length()!=n+3)
          return;

          if(i==5 && s1.length() == n+3)
          {
            sol.push_back(s1);
            return;
          }

          for(int j=1; start+j-1<n && j<=3; j++)
          {
                string temp = s.substr(start,j);
                if(isvalid(temp))
                {
                    string temp2 = s1;
                    if(i!=4)
                    s1=s1+temp+".";
                    else
                    s1=s1+temp;
                //    cout<<s1;
                    restoreAdd(s,n,s1,i+1,start+j);
                    s1 = temp2;
                }
                else
                continue;
          }
          return;
    }
    vector<string> restoreIpAddresses(string s)
    {
        int n=s.length();
        if(n>12)
        return sol;
        string s1="";
        restoreAdd(s,n,s1,1,0);
        return sol;
    }
};
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