Merge pull request #6220 from wlmb/challenges

Solve PWC168

3 files changed, 36 insertions, 0 deletions

diff --git a/challenge-168/wlmb/blog.txt b/challenge-168/wlmb/blog.txt
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+++ b/challenge-168/wlmb/blog.txt
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+https://wlmb.github.io/2022/06/06/PWC168/
diff --git a/challenge-168/wlmb/perl/ch-1.pl b/challenge-168/wlmb/perl/ch-1.pl
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+++ b/challenge-168/wlmb/perl/ch-1.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 168
+# Task 1: Perrin prime
+#
+# See https://wlmb.github.io/2022/06/06/PWC168/#task-1-perrin-prime
+use v5.12;
+use warnings;
+use bigint;
+use Math::Prime::Util qw(is_prime);
+die "Usage: $0 N\n to write the first N Perrin Primes" unless @ARGV;
+my $N=shift;
+my @last_perrins=(3,0,2);
+my @perrin_primes;
+my %seen;
+while(@perrin_primes<$N){
+    push @last_perrins, my $perrin=$last_perrins[-3]+$last_perrins[-2];
+    shift @last_perrins; # no need to keep old Perrins
+    $seen{$perrin}=1, push @perrin_primes, $perrin if is_prime($perrin) and !$seen{$perrin};
+}
+say join " ", sort {$a<=>$b} @perrin_primes;
diff --git a/challenge-168/wlmb/perl/ch-2.pl b/challenge-168/wlmb/perl/ch-2.pl
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+++ b/challenge-168/wlmb/perl/ch-2.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 168
+# Task 2: Home prime
+#
+# See https://wlmb.github.io/2022/06/06/PWC168/#task-1-perrin-prime
+use v5.12;
+use warnings;
+use Math::Prime::Util qw(is_prime factor);
+die "Usage: $0 n1 [n2... ]\n to obtain the home primes of n1..." unless @ARGV;
+for(@ARGV){
+    say("The argument ($_) should have been >=2"), next unless $_>=2;
+    my $N=$_;
+    $N=join "", factor($N) while(!is_prime($N));
+    say "HP$_=$N"
+}