Perl Solutions - Week 175

2 files changed, 71 insertions, 0 deletions

diff --git a/challenge-175/cheok-yin-fung/perl/ch-1.pl b/challenge-175/cheok-yin-fung/perl/ch-1.pl
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+++ b/challenge-175/cheok-yin-fung/perl/ch-1.pl
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+# The Weekly Challenge 175
+# Task 1 Last Sunday
+use v5.30.0;
+use Time::Local qw'timegm_nocheck';
+use Time::gmtime;
+
+
+say join "\n", last_sun_year($ARGV[0] || 2022)->@*;
+
+
+sub last_sun_month {
+    my ($m, $y)= @_;
+    my $n = gmtime timegm_nocheck 0, 0, 0, 1, $m+1, $y;
+    my $constant = $n->wday() == 0 ? 7 : $n->wday();
+    return (gmtime timegm_nocheck 0, 0, 0, 1-$constant, $m+1, $y);
+}
+
+
+
+sub date_str {
+    my $d_s = $_[0];
+    return 
+         ($d_s->year()+1900)."-"
+        .($d_s->mon()<=8 ? 0 : "").($d_s->mon()+1)."-"
+        .($d_s->mday()<10 ? 0 : "").($d_s->mday())
+}
+
+
+
+sub last_sun_year {
+    my $y = $_[0]-1900;
+    my @suns = map {last_sun_month($_, $y)} (0..10);
+    return [map {date_str $_} @suns, last_sun_month(-1, $y+1)];
+}
+
+
+use Test::More tests => 1;
+use Test::Deep;
+cmp_deeply 
+    last_sun_year(2022), 
+    ["2022-01-30",
+    "2022-02-27",
+    "2022-03-27",
+    "2022-04-24",
+    "2022-05-29",
+    "2022-06-26",
+    "2022-07-31",
+    "2022-08-28",
+    "2022-09-25",
+    "2022-10-30",
+    "2022-11-27",
+    "2022-12-25"];
diff --git a/challenge-175/cheok-yin-fung/perl/ch-2.pl b/challenge-175/cheok-yin-fung/perl/ch-2.pl
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+++ b/challenge-175/cheok-yin-fung/perl/ch-2.pl
@@ -0,0 +1,19 @@
+# The Weekly Challenge 175
+# Task 2 Perfect Totient Number
+use v5.20.0;
+use Math::Prime::Util qw/euler_phi/;
+
+my $p = 0;
+for (my $n0 = 3; $n0 < 1_000_000_000; $n0 += 2) {
+    my $n = $n0;
+    my $sum = 0;
+    do {
+        $n = euler_phi($n);
+        $sum += $n;
+    } until ($sum > $n0 || $n == 1);
+    if ($sum == $n0) {
+        say $n0;
+        $p++;
+    }
+    last if $p >= ($ARGV[0] || 20);
+}