OldPhoneKeypad

Using an old mobile phone keypad to convert a string of numeric inputs into readable text.

Function

• The program processes a string of key presses and it is converted into their corresponding letters.
• Each keys can be press multiple times but the input string must be end with # to be processed. If input string didn't consist of #, it will return nothing.
• Space key acts as a separator between character sequences.
• The * key acts as backspace.

Class and Method

Parameter

• input(string): A sequence of keys which ending with #

Implementation Details

1. Validation: If the input is null, empty, or does not end with #, an empty string is returned.
2. Removing the #: The last character is removed from the input.
3. Key Mapping: A dictionary maps numeric keys to their corresponding letters.
4. Processing Key Presses: Loops through each character into the input string. If a space is encountered, the previously processed letter is appended to the result.
5. Appending Final Character: After the loop, the last character is appended to the result.
6. Returning the Final String.

Example of Inputs & Outputs:

• Input: 33# -- > E
• Input: 4433555 555666# -- > HELLO