title: hash function for string
body: <p>I am looking for a hash function table for a set of short length strings (the length of each string is less than 50) with a special feature that whenever we search for a string in this table if the string is inside the table it returns the associated object of that string or specific and unique number, and if the string is not inside the table it gives the ID of very similar string to the input.
  in order to define similarity between two string, we can define different function, but let assume we define it as the minimum number of operation which needs to convert one string to another. 
  three note:</p>
  
  <ol>
  <li>the length of each inquiry string and saved string are always similar and fix.</li>
  <li>the alphabet of string are limited to only 5 different characters.</li>
  <li>off course memory and speed are both important for me.</li>
  </ol>
  
  <p>I am not looking for the final solution, but any suggestion or introducing some papers with similar approach in analogous condition are welcome. </p>