From b79c6b4d33d5bcf9289e499255d85ed92a0cb993 Mon Sep 17 00:00:00 2001 From: Kjetil S Date: Mon, 25 Jul 2022 19:24:43 +0200 Subject: https://theweeklychallenge.org/blog/perl-weekly-challenge-175/ --- challenge-175/kjetillll/perl/ch-1.pl | 10 ++++++++++ challenge-175/kjetillll/perl/ch-2.pl | 27 +++++++++++++++++++++++++++ 2 files changed, 37 insertions(+) create mode 100644 challenge-175/kjetillll/perl/ch-1.pl create mode 100644 challenge-175/kjetillll/perl/ch-2.pl diff --git a/challenge-175/kjetillll/perl/ch-1.pl b/challenge-175/kjetillll/perl/ch-1.pl new file mode 100644 index 0000000000..5137aca00d --- /dev/null +++ b/challenge-175/kjetillll/perl/ch-1.pl @@ -0,0 +1,10 @@ +#!/usr/bin/perl +use Time::Local; +my $y = shift || 1900+(localtime)[5]; +for my $m (1..12){ + for(reverse 1..31){ + is_sunday($y,$m,$_) and printf("%04d-%02d-%02d\n", $y, $m, $_) and last + } +} + +sub is_sunday{ my($y,$m,$d)=@_; (eval{ timegm(0,0,0,$d,$m-1,$y) } / 86400 - 3) % 7 == 0 } diff --git a/challenge-175/kjetillll/perl/ch-2.pl b/challenge-175/kjetillll/perl/ch-2.pl new file mode 100644 index 0000000000..5dc7946afe --- /dev/null +++ b/challenge-175/kjetillll/perl/ch-2.pl @@ -0,0 +1,27 @@ +#!/usr/bin/perl +# prints the first 20 Perfect Totient Numbers: +# 3 9 15 27 39 81 111 183 243 255 327 363 471 729 2187 +# https://theweeklychallenge.org/blog/perl-weekly-challenge-175/ +# https://en.wikipedia.org/wiki/Perfect_totient_number +# use Math::Prime::Util::GMP 'gcd'; # ...is faster, but not a core module +# use Math::Prime::Util::GMP 'totient'; # ...is screamingly fast! + +use strict; use warnings; +use Memoize; +memoize('totient'); #good idea, unless using GMP +#memoize('gcd'); #bad idea, runs slower + +sub totient { my $n=shift; 0+grep gcd($_,$n)==1, 1..$n-1 } + +sub gcd { my($a,$b)=@_;($a,$b)=($b,$a)if$a>$b;($a,$b)=($b%$a,$a)while$a;$b } + +my $want = shift() // 20; +my $try = 1; +while( $want > 0 ){ + my $sum = 0; + my $n = $try; + $sum += $n = totient($n) while $n>1; + print "$try\n" and $want-- if $sum == $try; + $try+=2; +} + -- cgit