her two are required for fast running times</p></li>
</ul>
</li>
<li><p>A perfect hash function has:</p>
<ul class="simple">
<li><p>No blanks (i.e., no empty cells)</p></li>
<li><p>No collisions</p></li>
</ul>
</li>
<li><p>Lookup table is at best logarithmic</p></li>
<li><p>We can‚Äôt just make a very large array - we assume the key space is too large</p>
<ul class="simple">
<li><p>you can‚Äôt just hash by social security number</p></li>
</ul>
</li>
<li><p><span class="math notranslate nohighlight">