Merging of duplicate path values of a Perl HOH - perl

Question

I have a perl HOH (hash of hash) wherein i have serial numbers 1,2,3.... so on and directory paths with associated counter values. Could anyone please suggest a way in which i can merge the duplicate internal paths (e.g, /usr/lib , /bin/ ) to a form a new hash with addition of the values?
Sample HOH:
$VAR1 = {
'1' => {
'/usr/lib' => 18
},
'3' => {
'/bin/' => '3'
},
'4' => {
'/usr/lib' => 12
},
'2' => {
'/bin/' => '6'
},
'5' => {
'/dev/' => '2'
},
'6' => {
'/tmp/' => '8'
}
};
Final output requirement i am looking for is a simple hash with combined values. No need of serial numbers:
$VAR1 = {
'/usr/lib' => '30',
'/bin/' => '9',
'/dev/' => '2',
'/tmp/' => '8'
};

Answer 1

Try
sub aggregate_counts {
my $HOH = shift;
my %out;
for my $h (values %$HOH) {
for my $k ( keys %$h) {
$out{$k} += $h->{$k};
}
}
\%out
}
Use this subroutine like aggregate_counts($hoh) to get hash reference in required format.
Complete Script for testing:
use strict;
use warnings;
sub aggregate_counts {
my $HOH = shift;
my %out;
for my $h (values %$HOH) {
for my $k ( keys %$h) {
$out{$k} += $h->{$k};
}
}
\%out
}
my
$VAR1 = {
'1' => {
'/usr/lib' => 18
},
'3' => {
'/bin/' => '3'
},
'4' => {
'/usr/lib' => 12
},
'2' => {
'/bin/' => '6'
},
'5' => {
'/dev/' => '2'
},
'6' => {
'/tmp/' => '8'
}
};
use Data::Dumper;
print Dumper(aggregate_counts($VAR1))
Output:
$VAR1 = {
'/dev/' => '2',
'/tmp/' => '8',
'/bin/' => 9,
'/usr/lib' => 30
};

Answer 2

This could help you:
use strict; use warnings;
use Data::Dumper;
my %hash = (
'1' => {
'/usr/lib' => 18
},
'3' => {
'/bin/' => '3'
},
'4' => {
'/usr/lib' => 12
},
'2' => {
'/bin/' => '6'
},
'5' => {
'/dev/' => '2'
},
'6' => {
'/tmp/' => '8'
}
);
my %result;
foreach my $key (keys %hash){
foreach my $inner (keys %{$hash{$key}}) {
$result{$inner} += $hash{$key}{$inner};
}
}
print Dumper(\%result);
Output:
$VAR1 = {
'/usr/lib' => 30,
'/bin/' => 9,
'/dev/' => 2,
'/tmp/' => 8
};
Note: Please post your code as well in the question while asking for a help in SO.

Answer 3

You don't care about the keys of the outer hash. So let's start with values(%$VAR1):
{ '/usr/lib' => 18 },
{ '/bin/' => '3' },
{ '/usr/lib' => 12 },
{ '/bin/' => '6' },
{ '/dev/' => '2' },
{ '/tmp/' => '8' },
Hashes are great for grouping. We're going to iterate over the above list, then we're going to iterates over the elements of each of those hashes, using a hash to group them.
my %grouped;
for my $inner (values(%$VAR1)) {
for my $key (keys(%$inner)) {
my $val = $inner->{$key};
$grouped{$key} += $val;
}
}
And we're already done.