Data structure behind T9 type of dictionary

Question

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...

Answer 1

I guess, as those before that T9 uses a trie, where the links are represented by a bitmap (1 bit per letter). This is called a succinct data structure, as Steve Hanov explains very nicely:

http://stevehanov.ca/blog/index.php?id=120