I'm not sure how your algorithm is different then mine. You start from the back, I start from the front, but if you compare the two side-by-side, they are almost identical.

My Original post - Non-Biased version Alokito's version Fisher-Yates Shuffle
my @lList = (1..10); my @a = (1 .. 10); my $array = shift;
my ($lPos, $lRand); print join("\t", @a),"\n"; my $i;
# For every position in the list, swap it with a random
# position earlier in the list.		 #starting from the end and working back
foreach $lPos (1..$#list) { for ($i = $#a; $i > 0; $i--) { for ($i = @$array; --$i; ) {
    # pick a random guy to stuff in the ith slot
    $lRand = int(rand($lPos+1));     $guy = int(rand($i + 1));     my $j = int rand ($i+1);
    #snatch the guy out, and stuff him in!     next if $i == $j;
    @lList$lPos, $lRand = @lList$lRand, $lPos;     splice(@a, $i, 0, splice(@a, $guy, 1));     @$array$i,$j = @$array$j,$i;
} } }
print join("\t", @a),"\n";

When I posted this, I had not realized it was so similar to the one in the faq, the fisher_yates_shuffle. The only real difference is fisher-yates does not allow an element to stay in the same position. I don't think this is necessary. If someone knows why this is done, I would love to learn it.

Alokito,
You seem to imply that my solution either does not randomize in place, or is biased. To quote:

Bah, all the solutions I have seen either violate the order not to create new lists, or seem to produce biased results. I think I have found a way to do neither.
But the truth is, our code does almost the same thing, just from different directions. Am I missing something?

In reply to RE: RE: Randomize List of items by johannz
in thread Randomize List of items by johannz

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