title: Intersection algorithm for two unsorted, small array
body: <p>I'm looking for an algorithm for intersection of two small, unsorted array in very specific condition.</p>
  
  <ul>
  <li>Type of array item is just integer or integer-like type.</li>
  <li>Significant amount of time (about 30~40%?), one or both array might be empty.</li>
  <li>Arrays are usually very small - usually 1~3 items, I don't expect more than 10.</li>
  <li>The intersection function will be called very frequently.</li>
  <li>I don't care about platform dependent solution - I'm working on x86/windows/C++</li>
  </ul>
  
  <p>Both brute-force/sort-and-intersect solutions are not that bad, but I don't think that they're fast enough. Is there more optimal solution?</p>