<h2><a href="https://leetcode.com/problems/letter-case-permutation/">784. Letter Case Permutation</a></h2><h3>Medium</h3><hr><div><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 = "a1b2"
<strong>Output:</strong> ["a1b2","a1B2","A1b2","A1B2"]
</pre>

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

<pre><strong>Input:</strong> s = "3z4"
<strong>Output:</strong> ["3z4","3Z4"]
</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>
</div>