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Mastering Modern Perl: Writing Efficient and Maintainable Code

Solution Review: Occurrences of a Subarray in an Array

Explore how to count the occurrences of a subarray inside a larger array in Perl. Understand using hashes to track frequencies and loops to iterate through arrays effectively, improving your grasp of Perl data structures and idiomatic coding.

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Solution

Let’s look at the solution before jumping into the explanation:

Perl
# @array and @sub_array are already defined.
my %counts;
# set the hash with undef values for @subarray keys only
undef @counts { @subarray };
foreach my $element (@array) {
    # increment for only those entries that are defined
    exists $counts{$element} and $counts{$element}++;
}
# loop for printing the counts hash
foreach my $element (@subarray) {
    print "$element = $counts{$element}. ";
}

Explanation

Let' ...