<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:
    bool isCorrect(string temp) {
        int i = 0;
        if(temp.back()=='.')
            return false;
        while (i < temp.length()) {
            if(temp[i]=='0'&& i<temp.length()-1 && temp[i+1]!='.'){
               return false;
            }
            if (temp[i] != '.') {
                int num = 0;
                while (i < temp.length() && temp[i] != '.') {
                    num = 10 * num + (temp[i] - '0');
                    if (num > 255)
                        return false;
                    ++i;
                }
            } 
            else {
                ++i;
            }
        }
        return true;
    }
    void recursion(string& s, string& temp, vector<string>& ans, int i,int &dots) {
        if (i>= s.length()) {
            if(dots==0 && isCorrect(temp))
                ans.push_back(temp);
            return;
        }
        if (dots <0) {
            return;
        }
        temp += s[i];
        temp += '.';
        --dots;
        recursion(s, temp, ans, i + 1, dots);
        temp.pop_back();
        ++dots;
        recursion(s, temp, ans, i + 1, dots);
        temp.pop_back();
    }
    vector<string> restoreIpAddresses(string s) {
        vector<string> ans;
        string temp="";
        int dots=3;
        recursion(s,temp,ans,0,dots);
        return ans;
    }
};
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