<p>The <strong>DNA sequence</strong> is composed of a series of nucleotides abbreviated as <code>'A'</code>, <code>'C'</code>, <code>'G'</code>, and <code>'T'</code>.</p>
<ul>
<li>For example, <code>"ACGAATTCCG"</code> is a <strong>DNA sequence</strong>.</li>
</ul>
<p>When studying <strong>DNA</strong>, it is useful to identify repeated sequences within the DNA.</p>
<p>Given a string <code>s</code> that represents a <strong>DNA sequence</strong>, return all the <strong><code>10</code>-letter-long</strong> sequences (substrings) that occur more than once in a DNA molecule. You may return the answer in <strong>any order</strong>.</p>