DAJ 198

3 files changed, 57 insertions, 0 deletions

diff --git a/challenge-198/dave-jacoby/blog.txt b/challenge-198/dave-jacoby/blog.txt
new file mode 100644
index 0000000000..98ad646bd9
--- /dev/null
+++ b/challenge-198/dave-jacoby/blog.txt
@@ -0,0 +1 @@
+https://jacoby.github.io/2023/01/03/mind-the-gap-weekly-challenge-198.html
\ No newline at end of file
diff --git a/challenge-198/dave-jacoby/perl/ch-1.pl b/challenge-198/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..412300592e
--- /dev/null
+++ b/challenge-198/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,29 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use experimental qw{ fc say postderef signatures state };
+
+my @examples = ( [ 1, 0, 3, 0, 0, 5 ], [ 2, 5, 8, 1 ], [3] );
+
+for my $e (@examples) {
+    my @list = $e->@*;
+    my $out  = max_gap(@list);
+    my $list = join ', ', @list;
+    say <<"END";
+    Input:  \@list = ($list)
+    Output: $out
+END
+}
+
+sub max_gap( @list ) {
+    return 0 if scalar @list < 2;
+    @list = sort @list;
+    my %hash;
+    for my $i ( 1 .. -1 + scalar @list ) {
+        my $gap = abs $list[$i] - $list[ $i - 1 ];
+        $hash{$gap}++;
+    }
+    my ($max) = sort { $b <=> $a } keys %hash;
+    return $hash{$max};
+}
diff --git a/challenge-198/dave-jacoby/perl/ch-2.pl b/challenge-198/dave-jacoby/perl/ch-2.pl
new file mode 100644
index 0000000000..044a2f68a4
--- /dev/null
+++ b/challenge-198/dave-jacoby/perl/ch-2.pl
@@ -0,0 +1,27 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use experimental qw{ say postderef signatures state };
+use Algorithm::Permute;
+
+my @examples = ( 10, 15, 1, 25 );
+
+for my $e (@examples) {
+    my $out = prime_count($e);
+    say <<"END";
+    Input:  \$n = $e
+    Output: $out
+END
+}
+
+# 1 is not a prime, but 2 is, but the regex in is_prime accepts 1, so
+# we start on 2 and go to the given max
+# grep ( is_prime($_) ) gives only the list of primes 
+# scalar gives us the count, which is what we want
+sub prime_count ( $e ) {
+    return scalar grep { is_prime($_) } 2 .. $e;
+}
+
+# https://catonmat.net/perl-regex-that-matches-composite-numbers
+sub is_prime ( $n ) { ( '1' x $n ) !~ /\A(11+?)\1+\z/ }