<p>Given an array of strings <code>nums</code> containing <code>n</code><strong>unique</strong> binary strings each of length <code>n</code>, return <em>a binary string of length </em><code>n</code><em> that <strong>does not appear</strong> in </em><code>nums</code><em>. If there are multiple answers, you may return <strong>any</strong> of them</em>.</p>
<strong>Explanation:</strong>"101" does not appear in nums. "000", "010", "100", and "110" would also be correct.
</pre>
<p> </p>
<p><strong>Constraints:</strong></p>
<ul>
<li><code>n == nums.length</code></li>
<li><code>1 <= n <= 16</code></li>
<li><code>nums[i].length == n</code></li>
<li><code>nums[i] </code>is either <code>'0'</code> or <code>'1'</code>.</li>
<li>All the strings of <code>nums</code> are <strong>unique</strong>.</li>