title: Create a hash map without original key values
body: <p>I have a file containing a list of couples. Each couple contains a 64 bit integer, that is an hash computed over a string, and a value that is an integer.</p>
  
  <p>I want to load the list in a hash map in the main memory.
  And then search values using the original string (I have the hash function). </p>
  
  <p>For Example the file could be like: </p>
  
  <pre><code>keys values
  78243536 12
  38735342 20
  32353498 18
  </code></pre>
  
  <p>if I want to search a term for example "pippo" I can use <code>hashfunction("pippo")</code>.</p>
  
  <p>The question is: can I use <code>std::map</code> computed on these hash? How can I insert directly the hash values inside the map without having the original string?</p>