title: Hashing std::vector independent of items order
body: <p>I am looking for a hash function for <code>std::vector</code>, which would be independent from vector's item's ordering.</p>
  
  <p>In other words I am looking for a hash implementation,
  that would give me same result for </p>
  
  <pre><code>std::vector&lt;int&gt; v1(1,2,3);
  std::vector&lt;int&gt; v2(2,3,1);
  std::vector&lt;int&gt; v3(1,3,2); 
  </code></pre>
  
  <p>Any ideas on how I might accomplish this?</p>