title: Address book and trie structure
body: <p>I'have a question for you. I have to implement a business address book that contains 30000 names. All the names contains firstname and lastname.
  I have to implement an autocomplete textbox that search not only typing firstname but also by lastname.
  Searching on google I've seen that this problem is solved using a patricia trie but it does only prefix search so if I create a trie with firstname+lastname how can I search not only by firstname but also by lastname?</p>
  
  <p>Do I have to duplicate entries inserting two strings like this?
  Firstname+lastname
  And
  Lastname+firstname</p>
  
  <p>Please help me!!!</p>
  
  <p>The search have to be very efficient.</p>
  
  <p>Thanks.</p>