Re: Efficient way of comparing items in an array

On Thu, 30 Oct 2008 16:04:31 +1000, Dave Tang <d.tang@xxxxxxxxxxxxx> wrote:

Hi everybody,

I am working with a sorted array (sorted from smallest to largest), containing coordinates as such:

13645692
13645693
13645694
13645695
13645696
13645697
13645698
13645699
13645700
13645701
13645702
13645703
13645704
13645705
13645706
13645707
13645708
13645709
13645710
13645711

If each element has a difference of 1 from the next element, I would like to connect them and for this example the output will be:

13645692 - 13645711

However sometimes the elements are not separated by 1 as such:

13645692
13645693
13645694
13645709
13645710
13645711

For this example the output would be:

13645692 - 13645694
13645709 - 13645711

I have written the following code but I wish I could think of a much better way of achieving my output. Any tips and suggestions will be greatly appreciated! Thanks in advance.

my $prev = 'NULL';
my $first = '';
for (my $i = 0; $i < scalar(@array); ++$i){
if ($prev eq 'NULL'){
$prev = $array[$i];
$first = $array[$i];
}
else {
if ($prev == $array[$i] + 1){
$prev = $array[$i];
}
else {
print "$first - $prev\n";
$prev = $array[$i];
$first = $array[$i];
}
}
}
print "$first - $prev\n";

__END__

Dave



Oops I mean (I wrote the code in my email) and sorry for the double post.

my $prev = 'NULL';
my $first = '';
for (my $i = 0; $i < scalar(@array); ++$i){
if ($prev eq 'NULL'){
$prev = $array[$i];
$first = $array[$i];
}
else {
if ($array[$i] == $prev + 1){
$prev = $array[$i];
}
else {
print "$first - $prev\n";
$prev = $array[$i];
$first = $array[$i];
}
}
}
print "$first - $prev\n";

__END__

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