@raw_data = sort @raw_data;
[download]

@raw_data = sort {$b <=> $a} @raw_data
[download]

This isn't even an EFFICIENT bubble sort (hehe), since "isSorted" could be done as part of the bubbling loop, by bubbling until no swaps occur. But this version is probably easier to read.

sub bubble {
   my $arrRef=shift;

   foreach my $i(1..@$arrRef-1) {
      @$arrRef[$i,$i-1]=@$arrRef[$i-1,$i] 
            unless $arrRef->[$i-1]<=$arrRef->[$i];
   }
}

sub isSorted {
   my $arrRef=shift;
   my $isSorted=0;

   foreach my $i(1..@$arrRef-1) {
      return 0 unless $arrRef->[$i-1]<=$arrRef->[$i];
   }

   return 1;
}

open(IN,"<raw_data") or die "Can't open raw_data, error $!";
my @raw_data=map {chomp;$_} <IN>;

print "Before sort: ",(join ",",@raw_data), "\n";
bubble(\@raw_data) while !isSorted(\@raw_data);
print "After sort: ",(join ",",@raw_data), "\n";
[download]

If this IS for homework, try to understand it before handing it in, k? Otherwise, your teacher's gonna ask you some tough questions, and you're going to be in deep trouble...

Besides, if your teacher likes perl enough to teach it, he probably hangs out here with us anyhow :)
--
Mike

Keep in mind that bubble sort is one of the worst known sorting approaches.

...for generalized data. for almost sorted data, it's the best algorithm. if you're maintaining a list of sorted data, adding a few items, and re-sorting, this may be the way to go.

~Particle ;Þ

Well, not really.

It's better than some, but you'd really want to do a selection or insertion sort to add your new elements, I think, depending on your data structure.

The problem is that bubble sort only ever moves an element 1 spot. So if you add an element that would normally go into position 1 of a 1000-item list at the end of the pre-sorted list, you're looking at 1000 iterations over the whole list to "bump" it up into position 1. Ouch...
--
Mike

Okay, here's a somewhat more efficient numeric bubble sort. (taking a list instead of arrayref, just like perl's sort.)

sub bubble {
    my @array = @_;
    for my $i (0..$#array) {
        for my $j (0..$i) {
            @array[$i, $j] = @array[$j, $i]
                if $array[$i] < $array[$j];
        }
    }
    return @array;
}
[download]



But:

Thou shalt not sort with bubbles!

Perl's sort is a lot easier, and a hell of a lot more efficient. If this is a homework assignment, and it probably is, don't just use our answers, but try to figure out WHY it works, and then tell your teacher real coders use sort instead.

If it's part of a job application test, make sure you're not dealing with talexb and go ahead with a more efficient sort.

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ByZWNvZ25pc2UgQmFzZTY0IHdoZW4
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