<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 {
   private:
    vector<string> res;
    vector<int> segs;
    void dfs(string& s, int part, int start) {
        if (part == 4) {
            // cout << part << segs[3] << endl;
            if (start == s.size()) {
                string temp;
                for (int i = 0; i < 4; i++) {
                    temp += to_string(segs[i]);
                    if (i < 3) temp += '.';
                }
                res.emplace_back(temp);
            }
            return;
        }

        if (start >= s.size()) return;
        if (s[start] == 0) return;

        int addr = 0;
        for (int end = start; end < s.size(); end++) {
            addr = addr * 10 + (s[end] - '0');
            if ((end > start && addr < 10) || addr > 255) break;
            // cout << part << ": "<< addr << endl;
            segs[part] = addr;
            dfs(s, part + 1, end + 1);
        }
    }

   public:
    vector<string> restoreIpAddresses(string s) {
        segs.resize(4, 0);
        dfs(s, 0, 0);
        return res;
    }
};
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