code:

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Function BWTDecode($sEncoded, $iOffset)
 
   ;Declare the variables
   Dim $iStringCounter,$iCounter,$sTransformVector
 
   ;Loop for each possible ANSI character
   For $iCounter=1 to 255
 
      ;Loop for each encoded character
      For $iStringCounter=1 to Len($sEncoded)
 
         ;If current ANSI = current encoded then 
         ;write down the position of the char (in encoded)
         ;This way the Transformation vector is determined
         If $iCounter=ASC(SubStr($sEncoded,$iStringCounter))
 
            ;Use a space as a delimiter
            $sTransformVector=$sTransformVector+" "+$iStringCounter
 
         EndIf
      Next
   Next
 
   ;Raise the offset by one; substr starts with 1 and not 0 (array index)
   $iOffset=$iOffset+1
 
   ;Loop to decode the encoded string
   For $iCounter=2 to $iStringCounter
 
      ;The output = the encoded string decoded using the offsets
      ;in the Transformation vector
      $BWTDecode=$BWTDecode+SubStr($sEncoded,$iOffset,1)
 
      ;Determine next offset
      $iOffset=Split($sTransformVector)[$iOffset]
   Next
EndFunction

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quote:

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Nice work documenting the code. You may also want to add that the TransformVector is also zero based like an ARRAY, but when we move to the string "one" base we need to increment the initial offset only. The TransformVector is already artificially high by one because of the initial space in $sTransformVector.

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