"""
Dictionary module for the keypad entry problem.

Author: Rodney Topor
Date: November 2007
"""

import string

# mapping from letters to digits
alpha_to_digit = string.maketrans(string.lowercase, 
                                  "22233344455566677778889999")
 
# dictionary mapping digit sequences to lists of words
digits_to_words = {}


def add_words(words):
    """Add each word in the list words to the dictionary."""
    for word in words:
        add_word(word)
      
        
def add_word(word):
    """Add a word to the dictionary."""
    # compute digit sequence corresponding to word
    digits = word.translate(alpha_to_digit)
    
    # add word to the list of words for this digit sequence
    if (digits_to_words.has_key(digits)):
        digits_to_words[digits].append(word)
    else:
        digits_to_words[digits] = [word]
 
        
def get_words(digits):
    """Return the list of words associated with a digit sequence."""
    if (digits_to_words.has_key(digits)):
        return digits_to_words[digits]
    else:
        return ["*" * len(digits)]