Merge pull request #5154 from wlmb/challenges

Add solution to pwc137

3 files changed, 46 insertions, 0 deletions

diff --git a/challenge-137/wlmb/blog.txt b/challenge-137/wlmb/blog.txt
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index 0000000000..3753e2a4c6
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+++ b/challenge-137/wlmb/blog.txt
@@ -0,0 +1 @@
+https://wlmb.github.io/2021/11/02/PWC137/
diff --git a/challenge-137/wlmb/perl/ch-1.pl b/challenge-137/wlmb/perl/ch-1.pl
new file mode 100755
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+++ b/challenge-137/wlmb/perl/ch-1.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 137
+# Task 1: Long year
+#
+# See https://wlmb.github.io/2021/11/02/PWC137/#task-1-long-year
+use v5.12;
+use warnings;
+use Text::Wrap qw(wrap $columns);
+use integer;
+$columns=62;
+say wrap("", "", grep {is_long_year($_)} ($ARGV[0]//1900..$ARGV[1]//2100));
+sub is_long_year {
+    my $YY=shift;
+    # Skip a day for every 'Gregorian' leap year extrapolating since 0000.
+    my $first_weekday=(($YY-1)+($YY-1)/4-($YY-1)/100+($YY-1)/400)%7; # 0=Monday
+    my $leap=$YY%400==0||$YY%4==0&&$YY%100!=0;
+    return $first_weekday==3 || $leap&&$first_weekday==2;
+}
diff --git a/challenge-137/wlmb/perl/ch-2.pl b/challenge-137/wlmb/perl/ch-2.pl
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+++ b/challenge-137/wlmb/perl/ch-2.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 137
+# Task 2: Lychrel number
+#
+# See https://wlmb.github.io/2021/11/02/PWC137/#task-2-lychrel-number
+use v5.12;
+use warnings;
+my ($lower, $upper, $maxcount, $largest)=(10,1000,500,10_000_000); #bounds
+foreach(@ARGV){
+    my @why=lychrel($_);
+    say "Input: $_\nOutput: ", @why?"0\n":"1?", @why>1?join("\n", @why):"";
+    say "";
+}
+sub lychrel {
+    my $n=shift;
+    my $r=reverse $n;
+    say("Failed $lower<=$_<=$upper"), exit unless $lower<=$_<=$upper;
+    my $count=$maxcount;
+    my @why=("as");
+    while(--$count){
+	return (@why) if $n eq $r;
+	push @why, "$n+$r=". ($n+=$r);
+	return if $n>=$largest;
+	$r=reverse $n;
+    }
+    return;
+}