<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> restoreIpAddresses(string s) {
        vector<string> res;
        vector<int> splitArray;
        restoreIpAddressesUtil(s, 0, s.length(), splitArray, res);
        return res;
    }

    void restoreIpAddressesUtil(string s, int start, int n, vector<int> &splitArray, vector<string> &res) {
        // If we've added 3 splits (which means 4 segments), we should validate
        if(splitArray.size() == 3) {
            if(start < n && checkIpAddresses(s, splitArray)) {
                string ipadrs = getIpAddresses(s, splitArray);
                res.push_back(ipadrs);
            }
            return;
        }

        // Generate splits by moving the start position forward
        for(int i = start; i < start + 3; i++) {
            splitArray.push_back(i + 1);
            restoreIpAddressesUtil(s, i + 1, n, splitArray, res);
            splitArray.pop_back();
        }
    }

    bool isValidSegment(const string& segment) {
        if (segment.empty() || segment.size() > 3 || (segment.size() > 1 && segment[0] == '0'))
            return false;
        int num = stoi(segment);
        return num >= 0 && num <= 255;
    }

    bool checkIpAddresses(const string& s, const vector<int>& splitArray) {
        return isValidSegment(s.substr(0, splitArray[0])) &&
            isValidSegment(s.substr(splitArray[0], splitArray[1] - splitArray[0])) &&
            isValidSegment(s.substr(splitArray[1], splitArray[2] - splitArray[1])) &&
            isValidSegment(s.substr(splitArray[2]));
    }

    string getIpAddresses(const string& s, const vector<int>& splitArray) {
        // Extract the four segments using the indices from splitArray
        string segment1 = s.substr(0, splitArray[0]);
        string segment2 = s.substr(splitArray[0], splitArray[1] - splitArray[0]);
        string segment3 = s.substr(splitArray[1], splitArray[2] - splitArray[1]);
        string segment4 = s.substr(splitArray[2]);

        // Concatenate the segments into an IP address format
        return segment1 + "." + segment2 + "." + segment3 + "." + segment4;
    }
};




// class Solution {
// public:
//     vector<string> restoreIpAddresses(string s) {
//         vector<string> res;
//         vector<int> splitArray;
//         restoreIpAddressesUtil(s, 0, s.length(), splitArray, res);
//         return res;
//     }

//     void restoreIpAddressesUtil(string s, int start, int n, vector<int> &splitArray, vector<string> &res) {
//         if(splitArray.size()>3) return;
//         if(splitArray.size()==3 && start<n) {
//             if(checkIpAddresses(s, splitArray)) {
//                 string ipadrs = getIpAddresses(s, splitArray);
//                 res.push_back(ipadrs);
//             }
//             return;
//         }
//         if(start==n) return;
//         for(int i=start;i<n;i++) {
//             splitArray.push_back(i);
//             restoreIpAddressesUtil(s, start+1, n, splitArray, res);
//             splitArray.pop_back();
//         }
//     }

//     bool isValidSegment(const string& segment) {
//         if (segment.empty() || segment.size() > 3 || (segment.size() > 1 && segment[0] == '0'))
//             return false;
//         int num = stoi(segment);
//         return num >= 0 && num <= 255;
//     }

//     bool checkIpAddresses(const string& s, const vector<int>& splitArray) {
//         return isValidSegment(s.substr(0, splitArray[0])) &&
//             isValidSegment(s.substr(splitArray[0], splitArray[1] - splitArray[0])) &&
//             isValidSegment(s.substr(splitArray[1], splitArray[2] - splitArray[1])) &&
//             isValidSegment(s.substr(splitArray[2]));
//     }

//     string getIpAddresses(const string& s, const vector<int>& splitArray) {
//         // Extract the four segments using the indices from splitArray
//         string segment1 = s.substr(0, splitArray[0]);
//         string segment2 = s.substr(splitArray[0], splitArray[1] - splitArray[0]);
//         string segment3 = s.substr(splitArray[1], splitArray[2] - splitArray[1]);
//         string segment4 = s.substr(splitArray[2]);

//         // Concatenate the segments into an IP address format
//         return segment1 + "." + segment2 + "." + segment3 + "." + segment4;
//     }
// };
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