<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>

static const int fast = []{
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(0);
    std::cout.tie(0);

    return 0;
}();
class Solution {
public:

    vector<string> Ans;

    void findAns(string s, string ans){
        if(s.size() == 0){
            Ans.push_back(ans);
            return;
        }
        if(isdigit(s[0])){
            findAns(s.substr(1) , ans + s[0]);
        }else{
            if(s[0] >= 'a' && s[0] <= 'z'){
                findAns(s.substr(1) , ans + s[0]);
                findAns(s.substr(1) , ans + static_cast<char>(s[0]-32));
            }else{
                findAns(s.substr(1) , ans + s[0]);
                findAns(s.substr(1) , ans + static_cast<char>(s[0]+32));
            }
        }
    }

    vector<string> letterCasePermutation(string s) {
        findAns(s , "");
        return Ans;
    }
};

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