20 lines
361 B
Perl
20 lines
361 B
Perl
use strict;
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use warnings;
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use tests::random;
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sub shuffle {
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my ($in, $cnt, $sz) = @_;
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$cnt * $sz == length $in or die;
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my (@a) = 0...$cnt - 1;
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for my $i (0...$cnt - 1) {
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my ($j) = $i + random_ulong () % ($cnt - $i);
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@a[$i, $j] = @a[$j, $i];
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}
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my ($out) = "";
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$out .= substr ($in, $_ * $sz, $sz) foreach @a;
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return $out;
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}
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1;
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