how to calculate efficent how many elements in a list are the same?
<p>I need to do the following task:</p>

<ul>
<li>I have a list with items. </li>
<li>Each of the items also have a List with strings like "<code>gkejgueieriug</code>"</li>
<li>Now I need to run throw the list and check how many of the items in the list of each item are also in the current element</li>
</ul>

<p>here is a small pseudeo code:</p>

<pre><code>OneItem;
List AllItems;
for Item in AllItems:
    int count = number strings in Item.Values which are also in OneItem.Values
</code></pre>

<p>because the data is very big, I need some help to make a efficent implementation.</p>

<p>How to do this? Should I use a hashmap? how to count the overlap?</p>
