You are working on the query preprocessor for your search engine. When a user submits a search query, the preprocessor must do the following:
- Remove all commonly used words. These words do not increase search quality.
- Remove all duplicate words. Each distinct word in the query must appear only once.
- Sort the remaining words in alphabetical order.
You are given a String query containing a single space separated list of words. You are also given a String common, each element of which is a commonly used word. Preprocess the query using the process described above and return the resulting list of words as a String.