27-C01P16

C01P16 - Nokia keypad

A long time ago, before the smartphones, when you had to write some messages, the keypads looked like that:

For example, on such keypad, if you want to write Ruby, you had to press the following sequence of numbers:

7778822999

Each key contains some letters from the alphabet. And by pressing that key, you rotate the letters until you get to your desired one.

It's time to implement some encode / decode functions for the old keypads!

First, implement a function that takes a list of integers - the sequence of numbers that have been pressed. The returned value should be the corresponding string of the message.

Signature

def numbers_to_message(pressed_sequence):
    pass

There are some special rules:

• If you press 1, the next letter is going to be capitalized
• If you press 0, this will insert a single white-space
• If you press a number and wait for a few seconds, the special breaking number -1 enters the sequence. This is the way to write different letters from only one keypad!

Examples:

>>> numbers_to_message([2, -1, 2, 2, -1, 2, 2, 2])
"abc"
>>> numbers_to_message([2, 2, 2, 2])
"a"
>>> numbers_to_message([1, 4, 4, 4, 8, 8, 8, 6, 6, 6, 0, 3, 3, 0, 1, 7, 7, 7, 7, 7, 2, 6, 6, 3, 2])
"Ivo e Panda"

Now it is time to convert the message to a sequence of numbers. This function takes a string - the message and returns the minimal keystrokes that you need to write that message

Signature

def message_to_numbers(message):
    pass

Examples

>>> message_to_numbers("abc")
[2, -1, 2, 2, -1, 2, 2, 2]
>>> message_to_numbers("a")
[2]
>>> message_to_numbers("Ivo e Panda")
[1, 4, 4, 4, 8, 8, 8, 6, 6, 6, 0, 3, 3, 0, 1, 7, 2, 6, 6, 3, 2]
>>> message_to_numbers("aabbcc")
[2, -1, 2, -1, 2, 2, -1, 2, 2, -1, 2, 2, 2, -1, 2, 2, 2]