<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> result;
    int isValid(string str) {
        int n = str.size();
        if (n < 7 || n > 15) return false;  // Quick check based on size constraints
        
        // Split the string by '.'
        vector<string> parts;
        stringstream ss(str);
        string part;
        while (getline(ss, part, '.')) {
            parts.push_back(part);
        }

        // There should be exactly 4 parts
        if (parts.size() != 4) return false;

        // Check each part
        for (string part : parts) {
            if (part.empty() || part.size() > 3) return false;

            // Check for leading zeros
            if (part[0] == '0' && part.size() > 1) return false;

            // Check if the part is a number and in range 0-255
            for (char ch : part) {
                if (!isdigit(ch)) return false;
            }

            int num = stoi(part);
            if (num < 0 || num > 255) return false;
        }

        return true;
    }
    void helper(string s, string curr, int i, int dots){
        if(s.size()==i) return;
        if(dots==0){
            curr+=s.substr(i);
            bool ans = isValid(curr);
            if(ans){
                result.push_back(curr);
            }
            return;
        }

        helper(s, curr+s[i], i+1, dots);
        helper(s, curr+".", i, dots-1);

    }
    vector<string> restoreIpAddresses(string s) {
        if(s.size()<4 or s.size()>12) return result;
         helper(s, "", 0, 3);
        return result;
    }
};
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