<p>Given a string <code>s</code>, you&nbsp;can transform every letter individually to be lowercase or uppercase to create another string.</p>

<p>Return <em>a list of all possible strings we could create</em>. Return the output in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;a1b2&quot;
<strong>Output:</strong> [&quot;a1b2&quot;,&quot;a1B2&quot;,&quot;A1b2&quot;,&quot;A1B2&quot;]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;3z4&quot;
<strong>Output:</strong> [&quot;3z4&quot;,&quot;3Z4&quot;]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 12</code></li>
	<li><code>s</code> consists of lowercase English letters, uppercase English letters, and digits.</li>
</ul>

#include <bits/stdc++.h>
using namespace std;

vector<string> theVector;
void permu (string s, int n) {
    if (n == s.size()) {
        theVector.push_back(s);
        return;
    } else {
        if (s[n] > '9') {
            s[n] = toupper(s[n]);
            permu(s, n + 1);
            s[n] = towlower(s[n]);
            permu(s, n + 1);
        } else permu(s, n + 1);
    }
}

class Solution {
public:
    vector<string> letterCasePermutation(string s) {
        permu(s, 0);
        vector<string> aVector = theVector;
        theVector.clear();
        return aVector;
    }
};
12800