looking for a tuple substitution algorihtm
<p>I was asked this question during an interview. I knew its a combinatorial problem but I have no idea how to solve this recursively. I am mostly looking for an approach to solving these kind of problems.</p>

<blockquote>
  <p>Given a Tuple for eg. (a, b, c)</p>
  
  <p>Output : <code>(*, *, *), (*, *, c), (*, b, *), (*, b, c), (a, *, *), (a, *, c),</code></p>

<pre><code>      (a, b, *), (a, b, c)
</code></pre>
</blockquote>
