C: How to detect a re-entry of a char character? : <blockquote>
  <p>I am creating a program whereby;
  the first input e.g.  'a'   will give a "no duplicate" result,
  and upon re-entry of 'a' it should would give me a "duplicate has found" result.</p>
</blockquote>

<pre><code>I am having a hard time finding the logic to this program. Help would be much appreciated. Thanks.
</code></pre>

<blockquote>
  <p>I am working on lines 127-129 btw. <a href="https://pastebin.com/wQKH3iZE" rel="nofollow noreferrer">https://pastebin.com/wQKH3iZE</a></p>
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