oldphonekeypad's Introduction

Old Phone Pad

This is a C# implementation of a method that converts a sequence of button presses on an old phone keypad to a string of letters.

The old phone keypad has the following layout:

  1     2     3
&'()  abc   def

  4     5     6
 ghi   jkl   mno

  7     8     9
pqrs  tuv   wxyz

  *     0     #
     space

To use the OldPhonePad method, simply call it with a string of button presses as input. The method will return the corresponding string of letters.

Example usage:

string output = OldPhonePad("227*#");
Console.WriteLine(output); // Output: B

Method signature

public static string OldPhonePad(string input)

Parameters

input: A string representing a sequence of button presses on an old phone keypad.

Return value

A string representing the corresponding sequence of letters.

Button mapping

The mapping of each button to its corresponding letters is as follows:

Button: 1
Letters: &'(

Button: 2
Letters: abc

Button: 3
Letters: def

Button: 4
Letters: ghi

Button: 5
Letters: jkl

Button: 6
Letters: mno

Button: 7
Letters: pqrs

Button: 8
Letters: tuv

Button: 9
Letters: wxyz

Button: *
Letters: (none)

Button: 0
Letters: space

Button: #
Letters: (none)

Additional notes

Pressing the same button repeatedly cycles through the letters associated with that button.
Pressing a different button or a pause before the end of the input adds the previous letter to the output.
The backspace button (*) removes the last letter from the output, unless it was the last character added to the output.
The pause button (0) adds a space to the output.
The end-of-input button (#) signals the end of the input and adds the last letter to the output.
If the input ends with a backspace button (*), the last letter added to the output is deleted and not included in the output.
If the input ends with a pause button (0) or a backspace button followed by a pause button (*0), the last letter is not included in the output.

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