title: Finding a duplicate numbers in an array and then counting the number of duplicates
body: <p>How would I take an array with long list of numbers that contains duplicates, so for instance:</p>
  
  <pre><code>NSArray *array = [NSArray arrayWithObjects:@"45", @"60", @"100",@"100", @"100", @"60"nil];
  </code></pre>
  
  <p>Just imagine that this is a HUGE list of random numbers. Now I'm sure that I have to use something like NSSet for this, but i'm not sure how to execute this. Also, once we identify the duplicates I'm guessing that I would then add those numbers to an array, and then call </p>
  
  <pre><code>[array count];
  </code></pre>
  
  <p>Any ideas?</p>