regular expression to find nth letter from end of string
<p>To find regular expression whether nth character in a string from the end is a character from the set <code>{a,e,i,o,u}</code>.</p>

<p>Eg:</p>

<pre><code>n=10;
String=algorithm
</code></pre>

<p>It is <code>true</code>. Since <code>a</code> is the tenth letter from the end is in the set.</p>

<pre><code>n=5;
abcdefg;
</code></pre>

<p>It is <code>false</code>. Since <code>c</code> is the fifth letter from the end.</p>

<p>How to identify an regular expression for the above pattern?</p>