Comparing 2 arrays in Perl

Question

Could someone provide a good /nice solution in Perl for comparing 2 arrays (a and b) which check if every element on array a is found in array b (and found only once in array b)?

Answer 1

See perlfaq4:

• How do I compute the difference of two arrays? How do I compute the intersection of two arrays?
• How do I test whether two arrays or hashes are equal?

Answer 2

Do you care if and item is b that not in a? The way you have it phrased b can have more items than a. Also, you need to specify what happens when an item is duplicated in an array. Here is some code that finds if there is at least one of every item in a in b:

#!/usr/bin/perl

use strict;
use warnings;

sub all_in_second {
    my ($first, $second) = @_;
    my %in_second        = map { $_ => 1 } @$second;

    for my $item (@$first) {
        return 0 unless $in_second{$item};
    }
    return 1;
}

my @a = (1, 2, 3, 3, 4);
my @b = (1, 2, 3, 4, 5);

print all_in_second(\(@a, @b)) ? "true" : "false", "\n";

@a = (1, 2, 3, 3, 6);
@b = (1, 2, 3, 4, 5);

print all_in_second(\(@a, @b)) ? "true" : "false", "\n";