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How do I shuffle an array randomly?by faq_monk (Initiate) |
on Oct 08, 1999 at 00:20 UTC ( [id://615]=perlfaq nodetype: print w/replies, xml ) | Need Help?? |
Current Perl documentation can be found at perldoc.perl.org. Here is our local, out-dated (pre-5.6) version: Use this:
# fisher_yates_shuffle( \@array ) : # generate a random permutation of @array in place sub fisher_yates_shuffle { my $array = shift; my $i; for ($i = @$array; --$i; ) { my $j = int rand ($i+1); next if $i == $j; @$array[$i,$j] = @$array[$j,$i]; } }
fisher_yates_shuffle( \@array ); # permutes @array in place You've probably seen shuffling algorithms that works using splice, randomly picking another element to swap the current element with:
srand; @new = (); @old = 1 .. 10; # just a demo while (@old) { push(@new, splice(@old, rand @old, 1)); }
This is bad because splice is already
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