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delphidelphi-xe2

Randomize StringList

How can I randomize the Strings in the StringList similarly how this online tool works. If anyone is familiar with it, check this: http://textmechanic.co/Randomize-List.html

Solution

  • One common algorithm to perform a shuffle is the Fisher-Yates shuffle. This generates uniformly distributed permutations.

    To implement on a Delphi TStrings object you can use this:

    procedure Shuffle(Strings: TStrings);
var
  i: Integer;
begin
  for i := Strings.Count-1 downto 1 do 
    Strings.Exchange(i, Random(i+1));
end;

    Now, whilst in theory this will generate uniformly distributed permutations, the actual performance depends heavily on the quality of the random number generator. This is discussed in Knuth's Art of Computer Programming, volume 2, section 3.4.2, Algorithm P.

    Further reading: