Find Dups from Array Itself

[perln00b]

I really new in Perl. I tried to create a simple script to
find the duplicate items in array. Here is my source code:
###########################################################
@arry = ("1", "2", "2", "2", "3", "3");
@dups = ();
@copiedArry = @arry;

$size = @arry;
$arryLoc = $size - 1;

for ($i=0; $i<=$arryLoc; $i++)
{
for ($j=0; $j<=$arryLoc; $j++)
{
while ($size != 0)
{
if($copiedArry[$i] eq $arry[$j]) # <==
{
push(@dups, $arry[$j]);
delete $arry[$j];
$size --;
}
else
{
$size --;
}
}
}
}

print "Here are the dups: \n";
foreach $data (@dups)
{
print $data ."\n";
}

##########################################################
see line with #<==, I got "Use of uninitialized value in string eq at
C:\Perl Projects\testing.pl line 17."
Is the way I created correct? Why I got "uninitialized value..." like that?

Thanks,
Lucas

 

[KevinADC]

I didn't try and debug your code since this is so much easier using a hash:

@arry = ("1", "2", "2", "2", "3", "3");
map {$dups{$_}++} @arry;

print "Here are the dups:\n";

for (keys %dups) {
   print "$dups{$_}\n" if $dups{$_} > 1;
}

I know for a newbie perl coder that probably looks like Greek. You have this:

delete $arry[$j];

delete() is for use with hashes, not arrays, so it isn't doing what you think/hope.

 

[TrojanWarBlade]

Try this:

#!/usr/bin/perl -w
use strict;
my @arry  = ("1", "2", "2", "2", "3", "3");
my %uniq  = ();
my @clean = grep { ! $uniq{$_}++;  } @arry;
print "Cleaned array is [@clean]\n";
my @dups  = map { $uniq{$_} > 1 ? ($_) : (); } sort keys %uniq;
print "Dupes are [@dups]\n";

Trojan.

 

[TrojanWarBlade]

Alert! Alert! Race condition!
;-)


Trojan.

 

[perln00b]

Thank you, guys.
Both scripts are working great.


Lucas

 

[KevinADC]

hehehe... did I win a prize for being first?

 

[TrojanWarBlade]

Nope, I won, I got the beer!



Trojan.

 

[KevinADC]

Figures, when I win the race, the prize is for being second... thats the story of my life!

 

[kordaff]

Delete actually works on arrays, hashes, array slices and hash slices since about perl 5.004 or 5.005 iirc...

Kordaff

 

[KevinADC]

delete() sort of works on an array, but it probably is not doing what a person thinks:

my @array = ('a'  .. 'z');
print "@array\n";
print scalar @array; [b]# prints 26[/b]
delete $array[0];
print scalar @array; [b]# still prints 26[/b]
print "@array";

basically turns the deleted scalar into an empty string.
for a hash it works like expected:

%hash = ();
map {$hash{$_}++} ('a'..'z');
print scalar keys %hash; [b]#prints 26[/b]
print "$_\n" for sort keys %hash;
delete $hash{a};
print scalar keys %hash; [b]#prints 25[/b]
print "$_\n" for sort keys %hash;

the hash key/value are deleted

 

[kordaff]

Ahh, only shrinks if it's last item in array. That's a lil broken heh. Best use splice then.

Kordaff