Part3T9 Clld mobile phone only has numerical keypads where every letter is associated with a number as shown below. Number 0 is designated as the spacebar. Since writing is tedious in old mobile pho ne, T9 system is created as the predictive text technology for mobile phone. It works as follows: I Every word is composed of letters. a Every letter can be mapped to a digit. o Given a series of digit from keyp resses, we can find the expected word. We can represent the keypad in two different ways: TUV . . . . . 1. A lIst such that each element Is a string of characters associated with the a number which is the element's index. Thisgives us: [" \