Telephone Texting

2021-11-29.py

question = """
Given a string containing digits from 2-9, return all possible letter combinations 
that the number could represent based on phone numbers/letters. For example, 
2 could be a, b, or c, 3 could be d, e, or f, and so on.

Example:

$ phoneLetter('9')
$ ['w', 'x', 'y', 'z']

$ phoneLetter('23')
$ ['ad', 'ae', 'af', 'bd', 'be', 'bf', 'cd', 'ce', 'cf']

"""
def phoneLetter(string):
    key_to_letter = {}
    key_to_letter['2'] = [ 'a', 'b', 'c' ]
    key_to_letter['3'] = [ 'd', 'e', 'f' ]
    key_to_letter['4'] = [ 'g', 'h', 'i' ]
    key_to_letter['5'] = [ 'j', 'k', 'l' ]
    key_to_letter['6'] = [ 'm', 'n', 'p' ]
    key_to_letter['7'] = [ 'p', 'q', 'r', 's' ]
    key_to_letter['8'] = [ 't', 'u', 'v' ]
    key_to_letter['9'] = [ 'w', 'x', 'y', 'z' ]
    
    output = []
    for ch in string:
        if len(output) == 0:
            for letter in key_to_letter[ch]:
                output.append(letter)
        else:
            new = []
            for letter in key_to_letter[ch]:
                for added in list(map(lambda x: x + letter, output)):
                    new.append(added)
            output = new
    return output

print(phoneLetter('9'))
print(phoneLetter('23'))