Recently, I have been participating in Mohammad Anwar’s Perl Weekly Challenge. Last week I solve in Perl and Elm… and live streamed it via Twitch and uploaded to Youtube.
This week, despite not feeling great I took a stab at the “Min Sliding Window” challenge over at https://perlweeklychallenge.org/blog/perl-weekly-challenge-073/ in #Perl.
I try and do these challenges in a TDD(ish) style. This week I did not do great; not feeling 100% well I cut some corners and spun my wheels quite a bit. However, I got there in the end.
Getting started.
I’ve used challenges like this as opportunities to keep my coding skills from getting too rusty quite a bit over time so I have a “methodology” I tend to use.
I start with a Test2::V0 test file which starts off looking like this:
use Test2::V0 -target => 'Sliding';
done_testing;
This fails straight out of the box, as the library does not exist yet. So I create a .pm file:
package Sliding;
1;
From then, I start building out tests; then library in the traditional Red/Green loop. And thats how I do it; and it looks like this:
use Test2::V0 -target => 'Sliding';
subtest 'min_from_windows example' => sub {
my @array = ( 1, 5, 0, 2, 9, 3, 7, 6, 4, 8 );
my $window_size = 3;
my @expected = ( 0, 0, 0, 2, 3, 3, 4, 4 );
is $CLASS->min_from_windows(
array_of_numbers => \@array,
window_size => $window_size,
),
\@expected;
};
subtest 'min_from_windows test two' => sub {
my @array = ( 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, );
my $window_size = 3;
my @expected = ( 0, 1, 2, 3, 4, 5, 6, 7 );
is $CLASS->min_from_windows(
array_of_numbers => \@array,
window_size => $window_size,
),
\@expected;
};
subtest 'min_from_windows test three' => sub {
my @array = ( 0, 1, 2, 3, 4, 5 );
my $window_size = 2;
my @expected = ( 0, 1, 2, 3, 4 );
is $CLASS->min_from_windows(
array_of_numbers => \@array,
window_size => $window_size,
),
\@expected;
};
subtest 'min_from_windows test three' => sub {
my @array = ( 99, 1, 32, 4, 5, 5 );
my $window_size = 2;
my @expected = ( 1, 1, 4, 4, 5 );
is $CLASS->min_from_windows(
array_of_numbers => \@array,
window_size => $window_size,
),
\@expected;
};
done_testing;
And the library looks like this:
package Sliding;
use List::Util 'min';
sub min_from_windows {
my ($self, %args) = @_;
my @numbers = @{$args{array_of_numbers}};
my $length = @numbers;
my $the_end = $length - $args{window_size};
my @array_of_mins;
for my $i (0 .. $the_end){
my @slice = @numbers[$i .. ($i-1) + $args{window_size}];
push @array_of_mins, min @slice;
}
return \@array_of_mins;
}
1;
As I have said to Mohammad on the stream a few times; I am not doing this as well as potentially I could/should. For example I have not validated my inputs. In this case I’ve not even turned it into a script as per the instructions.
Participating is not restricted to Perl; as I said I have done it in Elm. So, even if you are not a Perl developer you can give it a go.
Just pop over to https://perlweeklychallenge.org and see what is required and give it a shot.
Lance
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