Done with 159

3 files changed, 73 insertions, 0 deletions

diff --git a/challenge-159/dave-jacoby/blog.txt b/challenge-159/dave-jacoby/blog.txt
new file mode 100644
index 0000000000..7e8bde9c00
--- /dev/null
+++ b/challenge-159/dave-jacoby/blog.txt
@@ -0,0 +1 @@
+https://jacoby.github.io/2022/04/04/mtal-perlant-weekly-challenge-159.html
diff --git a/challenge-159/dave-jacoby/perl/ch-1.pl b/challenge-159/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..1cbd72e7df
--- /dev/null
+++ b/challenge-159/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,31 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say postderef signatures state };
+no warnings qw{ experimental };
+
+use Carp;
+use Getopt::Long;
+
+my $n = 6;
+GetOptions( 'number=i' => \$n, );
+croak 'Out of range' if $n < 1;
+
+farey($n);
+
+sub farey ( $i ) {
+    my %farey;
+    for my $d ( 1 .. $i ) {
+        for my $n ( 0 .. $d ) {
+            my $k = eval( $n / $d );
+            $farey{$k} = qq{$n/$d} unless defined $farey{$k};
+        }
+    }
+    my $output = join ', ', map { $farey{$_} } sort { $a <=> $b } keys %farey;
+
+    say <<"END";
+Input:  \$n = $i
+Output: $output.
+END
+}
diff --git a/challenge-159/dave-jacoby/perl/ch-2.pl b/challenge-159/dave-jacoby/perl/ch-2.pl
new file mode 100644
index 0000000000..8153825005
--- /dev/null
+++ b/challenge-159/dave-jacoby/perl/ch-2.pl
@@ -0,0 +1,41 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say postderef signatures state };
+no warnings qw{ experimental };
+
+use utf8;
+
+for my $n ( 1 .. 50 ) {
+    my $μ = möbius($n);
+    print join " ", "  " , map { sprintf '%2d', $_ } $n, $μ;
+    say '' if $n % 10 == 0;
+}
+
+sub möbius ($n) {
+    my @primes = prime_factors($n);
+    my %primes;
+
+    # has squared prime factor
+    map { $primes{$_}++ } @primes;
+    for my $k ( keys %primes ) {
+        return 0 if $primes{$k} > 1;
+    }
+
+    # square-free
+    my $p = scalar @primes;
+    return $p % 2 == 0 ? 1 : -1;
+}
+
+sub prime_factors( $n ) {
+    my @primes;
+    my $nn = $n;
+    for my $i ( 2 .. $n ) {
+        while ( $nn % $i == 0 ) {
+            $nn = $nn / $i;
+            push @primes, $i;
+        }
+    }
+    return @primes;
+}