Perl: find the max and min values in the array of hashes - arrays

Question

I have the structure below in Perl:
#!/usr/bin/perl
use strict;
use warnings;
my %hash = (
'firstitem' => {
'1' => ["A","99"],
'2' => ["B","88"],
'3' => ["C","77"],
},
'seconditem' => {
'3' => ["C","100"],
'4' => ["D","200"],
'5' => ["E","300"],
},
);
I am looking for a way to find the max number and min number in the array of each hash.
So the output will be
firstitem: max:99, min:77
seconditem: max:300, min:100
My idea is sorting the secondary key first and then do the bubble sort or other sorts in the for loop. It looks like not very elegant and smart.
foreach my $k1 (keys %hash) {
my $second_hash_ref = $hash{$k1};
my #sorted_k2 = sort { $a <=> $b } keys %{$second_hash_ref};
foreach my $i (0..$#sorted_k3){
#bubble sort or other sort
}
}

Answer 1

List::Util is a core module that provides the min and max functions:
use strict;
use warnings;
use List::Util qw(min max);
my %hash = (
'firstitem' => {
'1' => ["A","99"],
'2' => ["B","88"],
'3' => ["C","77"],
},
'seconditem' => {
'3' => ["C","100"],
'4' => ["D","200"],
'5' => ["E","300"],
},
);
for my $key (keys(%hash)) {
my #numbers = map { $_->[1] } values(%{$hash{$key}});
printf("%s: max: %d, min: %d\n", $key, max(#numbers), min(#numbers));
}
Output:
firstitem: max: 99, min: 77
seconditem: max: 300, min: 100

Answer 2

You are almost there.
Once you get to the second level what you need is the whole list of numbers, so to be able to find max and min of the lot. Since you need the extreme values for all arrays within the subkey you don't need to iterate over the second-level keys.
Also, you can fetch all array content unless the number is guaranteed to be at the specific place. Then use grep with Scalar::Util::looks_like_number to filter out elements that aren't numbers.
Finally, there is no benefit in sorting the keys.
use warnings;
use strict;
use feature 'say';
use Scalar::Util 'looks_like_number';
use List::MoreUtils 'minmax';
my %hash = (
'firstitem' => {
'1' => ["A","99"], '2' => ["B","88"], '3' => ["C","77"],
},
'seconditem' => {
'3' => ["C","100"], '4' => ["D","200"], '5' => ["E","300"],
},
);
foreach my $k1 (keys %hash)
{
my #nums =
grep { looks_like_number($_) }
map { #{ $hash{$k1}{$_} } }
keys %{$hash{$k1}};
my ($min, $max) = minmax #nums;
say "$k1: max = $max, min = $min";
}
This prints the expected values. If your real hash is exactly as shown you can extract arrayrefs directly by values %{$hash{$k1}}, with map { #$_ } to dereference them.
Since you need both extremes a good fit is minmax from List::MoreUtils, which is "the most efficient possible algorithm" for the job. The algorithm's performance is fully realized in the XS version of the module while the Perl version has some overhead.
Also note the core List::Util module, where individual min and max are, among other utilities.