Search whether AoH value exists in same Hash - perl

Question

I have hash which contains some data.
I want my final %hash to be printed like this:
'UGroup=1' => [ 'C72', 'C73', 'C71' ]
Here is my script:
use Data::Dumper;
my %h = (
'C72' => [ 'S=2-1' ],
'C73' => [ 'S=3-1' ],
'C71' => [ 'S=91-1'],
'UGroup=1' => [ 'S=1-1',
'S=2-1',
'S=3-1',
'S=91-1'],
);
print Dumper(\%h);
foreach my $C (sort keys %h) {
next unless $C =~ /UGroup/;
for my $f (#{$h{$C}}){
print "\tf:$f\n";
#This is not correct, but wanted to do something like this.
push #{$hash{$C}}, $f if(exists $h{$f});
}
}
print Dumper(\%hash);
Here in example input hash I need to check if S=91-1 has any key? If yes then associate that key to value for %hash with its original key.
How can I do that?

Answer 1

You didn't name the things, so
S=91-1 shall be a snake,
C71 shall be a cow, and
UGroup=1 shall be a group.
Start by building this hash:
my %cows_by_snake = (
'S=91-1' => [ 'C71' ],
'S=2-1' => [ 'C72' ],
'S=3-1' => [ 'C73' ],
);
Just ignore the keys that of %h that are groups when you do so.
Once you built a hash, it's simply a question of doing the following:
Create an empty result hash.
For each group,
Create an empty collection of cows.
For each snake associated the the group,
Add the cows associated with the snake to the collection.
Eliminate the duplicates in the collection of cows.
Add the group and the associated cows to the result hash.
my #groups;
my #cows;
for my $cow_or_group (keys(%h)) {
if ($cow_or_group =~ /^UGroup=/) {
push #groups, $cow_or_group;
} else {
push #cows, $cow_or_group;
}
}
my %cows_by_snake;
for my $cow (#cows) {
for my $snake (#{ $h{$cow} }) {
push #{ $cows_by_snake{$snake} }, $cow;
}
}
my %results;
for my $group (#groups) {
my %group_cows;
for my $snake (#{ $h{$group} }) {
for my $cow (#{ $cows_by_snake{$snake} }) {
++$group_cows{$cow};
}
}
$results{$group} = [ sort keys %group_cows ];
}