Solve PWC175

3 files changed, 36 insertions, 0 deletions

diff --git a/challenge-175/wlmb/blog.txt b/challenge-175/wlmb/blog.txt
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+++ b/challenge-175/wlmb/blog.txt
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+https://wlmb.github.io/2022/07/25/PWC175/
diff --git a/challenge-175/wlmb/perl/ch-1.pl b/challenge-175/wlmb/perl/ch-1.pl
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+++ b/challenge-175/wlmb/perl/ch-1.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 175
+# Task 1: Last Sunday
+#
+# See https://wlmb.github.io/2022/07/25/PWC175/#task-1-last-sunday
+use v5.36;
+use DateTime;
+die "Usage: $0 Y1 [Y2...]\nto print the last Sundays of years Y1, Y2...\n"
+    unless @ARGV;
+foreach my $year(@ARGV){
+    say "\nLast Sundays of year $year:";
+    say $_->subtract(days=>$_->day_of_week%7)->ymd for
+        map {DateTime->last_day_of_month(year=>$year, month=>$_)} (1..12)
+}
diff --git a/challenge-175/wlmb/perl/ch-2.pl b/challenge-175/wlmb/perl/ch-2.pl
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+++ b/challenge-175/wlmb/perl/ch-2.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 175
+# Task 2: Perfect totient numbers
+#
+# See https://wlmb.github.io/2022/07/25/PWC175/#task-2-perfect-totient-numbers
+use v5.36;
+use List::Util qw(sum);
+use Math::Prime::Util qw(euler_phi);
+die "Usage: $0 N\nto print the first N perfect totient numbers\n"
+    unless @ARGV;
+say "$_: ", next_perfect_totient() for(1..shift);
+sub next_perfect_totient{
+    state $current=1;
+    ++$current;
+    ++$current until $current==sum recursive_totients($current);
+    $current
+}
+sub recursive_totients($m){ #(totient(m), totient(totient($m))...)
+    my $t=euler_phi($m);
+    $m==2?($t):(recursive_totients($t), $t)
+}