title: Data structure behind T9 type of dictionary
body: <p>How does a T9 dictionary work? What is the data structure behind it. If we type '4663' we get 'good' when we press down button we get 'gone' then 'home' etc...</p>
  
  <p>EDIT: If the user types in 46 then it should show 'go' and when pressed down arrow should show 'gone' etc...</p>