How do I compare key from one hash with values from other?

mug has asked for the wisdom of the Perl Monks concerning the following question:

I have two hashes. The keys of %hash1 are values in %hash2. %hash2 can have multiple values for the same key. I want to find the missing set of values (that is, keys of %hash1) for each key in %hash2.

Example:

my %hash1 = (
    A => 5,
    B => 7,
    C => 2,
    D => 8,
);
my %hash2 = (
    1234 => "A,C",
    4567 => "A,B,D",
    5678 => "C",
);
[download]

Originally posted as a Categorized Question.

Comment on How do I compare key from one hash with values from other? Download Code

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Re: How do I compare key from one hash with values from other? by 2501 (Pilgrim) on Dec 06, 2001 at 21:08 UTC
I am not quite sure I understood your question. Try this out..I think this kludge might be what you are looking for. `use strict; my %hash1 = ( A => 5, B => 7, C => 2, D => 8, ); my %hash2 = ( 1234 => "A,C", 4567 => "A,B,D", 5678 => "C", ); my %hash3; foreach my $key2 ( keys %hash2 ) { my %temphash = %hash1; foreach ( split /,/, $hash2{$key2} ) { delete $temphash{$_}; $hash3{$key2}= join ',', sort keys %temphash; } } foreach my $key ( keys %hash3 ) { print "$key : $hash3{$key}\n"; }` [download]	[reply] [d/l]
Re: How do I compare key from one hash with values from other? by aspect_khaliq (Novice) on Jan 18, 2007 at 11:00 UTC
This will print missing set of values for keys from Hash1. `use strict; my %hash1 = ( A => 5, B => 7, C => 2, D => 8, ); my %hash2 = ( 1234 => "A,C", 4567 => "A,D", 5678 => "C", ); my @a = split ",", join ',', values %hash2; my $found = 0; foreach my $key ( keys %hash1 ) { $found = 0; foreach my $val ( @a ) { $found = 1 if $val eq $key; } print "$key => $hash1{$key}\n" if !$found; }` [download] Output: `B => 7` [download]	[reply] [d/l] [select]
Re: How do I compare key from one hash with values from other? by jdporter (Paladin) on Jan 18, 2007 at 16:00 UTC
Well, you said "for each hash2 key", not "for all hash2 keys", so my solution is a bit different from the previous ones. `use strict; my %hash1 = ( A => 5, B => 7, C => 2, D => 8, ); my %hash2 = ( 1234 => "A,C", 4567 => "A,B,D", 5678 => "C", ); while ( my( $key2, $val2 ) = each %hash2 ) { my %keys1; @keys1{ split /,/, $val2 } = (); my @missing = grep { not exists $keys1{$_} } keys %hash1; print "hash2 key '$key2' is missing values '@missing'\n"; }` [download]	[reply] [d/l]