Merge pull request #5695 from jacoby/master

Challenge #153

3 files changed, 58 insertions, 0 deletions

diff --git a/challenge-153/blog.txt b/challenge-153/blog.txt
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+++ b/challenge-153/blog.txt
@@ -0,0 +1 @@
+https://jacoby.github.io/2022/02/21/luck-is-not-a-factor-weekly-challenge-153.html
diff --git a/challenge-153/dave-jacoby/perl/ch-1.pl b/challenge-153/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..5a58b7f2b2
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+++ b/challenge-153/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,24 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say postderef signatures state };
+no warnings qw{ experimental };
+
+use List::Util qw{ sum0 product };
+
+say join ', ', map { left_factorial($_) } 1 .. 10;
+
+# Left factorials: !n = Sum_{k=0..n-1} k!.
+sub left_factorial( $n ) {
+    return sum0 map { factorial($_) } 0 .. $n - 1;
+}
+
+sub factorial ( $n ) {
+    return 1 if $n == 0;
+    state $factorials ;
+    if ( !$factorials->{$n} ) {
+        $factorials->{$n} = product 1 .. $n;
+    }
+    return $factorials->{$n};
+}
diff --git a/challenge-153/dave-jacoby/perl/ch-2.pl b/challenge-153/dave-jacoby/perl/ch-2.pl
new file mode 100644
index 0000000000..2cb74e5455
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+++ b/challenge-153/dave-jacoby/perl/ch-2.pl
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+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say postderef signatures state };
+no warnings qw{ experimental };
+
+use List::Util qw{ sum0 product };
+
+@ARGV = ( 123, 145 ) unless scalar @ARGV;
+
+for my $i (@ARGV) {
+    my $f = is_factorion($i);
+    say join "\t", '', $i, $f;
+}
+
+sub is_factorion ( $n ) {
+    my $f = factorion($n);
+    return $f == $n ? 1 : 0;
+}
+
+sub factorion ( $n ) {
+    return sum0 map { factorial($_) } split //, $n;
+}
+
+sub factorial ( $n ) {
+    return 1 if $n == 0;
+    state $factorials ;
+    if ( !$factorials->{$n} ) {
+        $factorials->{$n} = product 1 .. $n;
+    }
+    return $factorials->{$n};
+}