How to resolve the algorithm Run-length encoding step by step in the AutoHotkey programming language

Published on 12 May 2024 09:40 PM
#Autohotkey

How to resolve the algorithm Run-length encoding step by step in the AutoHotkey programming language

Table of Contents

Problem Statement

Given a string containing uppercase characters (A-Z), compress repeated 'runs' of the same character by storing the length of that run, and provide a function to reverse the compression. The output can be anything, as long as you can recreate the input with it.

Note: the encoding step in the above example is the same as a step of the Look-and-say sequence.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Run-length encoding step by step in the AutoHotkey programming language

Source code in the autohotkey programming language

MsgBox % key := rle_encode("WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW")
MsgBox % rle_decode(key)

rle_encode(message)
{
  StringLeft, previous, message, 1
  StringRight, last, message, 1
  message .= Asc(Chr(last)+1)
  count = 0
  Loop, Parse, message
  {
    If (previous == A_LoopField)
      count +=1
    Else
    {
      output .= previous . count
      previous := A_LoopField 
      count = 1
    }
  }
  Return output
}

rle_decode(message)
{
  pos = 1
  While, item := RegExMatch(message, "\D", char, pos)
  {
    digpos := RegExMatch(message, "\d+", dig, item)
    Loop, % dig
      output .= char
    pos := digpos 
  }
  Return output
}

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