Re: How do I shuffle an array?

The Fisher-Yates shuffle is easy to code up:

# randomly permutate @array in place
sub fisher_yates_shuffle
{
    my $array = shift;
    my $i = @$array;
    while ( --$i )
    {
        my $j = int rand( $i+1 );
        @$array[$i,$j] = @$array[$j,$i];
    }
}

fisher_yates_shuffle( \@array );    # permutes @array in place
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Comment on Re: How do I shuffle an array? Download Code

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Re: Answer: How do I shuffle an array? by runrig (Abbot) on Aug 21, 2002 at 16:40 UTC
And mentioned numerous times in numerous places, the '`next if $i == $j`' is unnecessary, as it rarely saves an element swap (except on the smallest of arrays), so it actually costs more to do the comparison every time rather than just swapping unconditionally. BTW, in case anyone was wondering who these guys Fisher and Yates were, here's some links. They're hard to find when almost every reference to Fisher and Yates (and especially with the term 'shuffle') on Google is a perl reference :-)	[reply] [d/l]

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Re: Answer: How do I shuffle an array?
by runrig (Abbot) on Aug 21, 2002 at 16:40 UTC

next if $i == $j

BTW, in case anyone was wondering who these guys Fisher and Yates were, here's some links. They're hard to find when almost every reference to Fisher and Yates (and especially with the term 'shuffle') on Google is a perl reference :-)

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