133

3 files changed, 76 insertions, 0 deletions

diff --git a/challenge-133/dave-jacoby/blog.txt b/challenge-133/dave-jacoby/blog.txt
new file mode 100644
index 0000000000..651f56428e
--- /dev/null
+++ b/challenge-133/dave-jacoby/blog.txt
@@ -0,0 +1 @@
+https://jacoby.github.io/2021/10/05/mr-smith-squares-off-the-weekly-challenge-133.html
\ No newline at end of file
diff --git a/challenge-133/dave-jacoby/perl/ch-1.pl b/challenge-133/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..84060a3f87
--- /dev/null
+++ b/challenge-133/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,27 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say signatures state };
+no warnings qw{ experimental };
+
+my @examples = ( 10, 27, 85, 101 );
+
+for my $e (@examples) {
+    say join "\t", '', $e, isqrt1($e), isqrt2($e),;
+}
+
+# the way we're requested to not use, for demonstration
+sub isqrt1 ($n) {
+    return int sqrt $n;
+}
+
+# another way:
+sub isqrt2 ($n) {
+    my $j = 1;
+    while (1) {
+        return $j - 1 if $n < $j**2;
+        $j++;
+    }
+    return 1;
+}
diff --git a/challenge-133/dave-jacoby/perl/ch-2.pl b/challenge-133/dave-jacoby/perl/ch-2.pl
new file mode 100644
index 0000000000..9b8be257f5
--- /dev/null
+++ b/challenge-133/dave-jacoby/perl/ch-2.pl
@@ -0,0 +1,48 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say signatures state };
+no warnings qw{ experimental };
+
+use List::Util qw{ sum sum0 };
+my @from_wikipedia = ( 4, 22, 27, 58, 85, 95, 121 );
+my %from = map { $_ => 1 } @from_wikipedia;
+
+my @smith_numbers = get_smith_numbers();
+
+say join ', ', @smith_numbers;
+
+exit;
+
+sub sum_of_digits ( $n ) { return sum split //, $n }
+
+sub sum_of_factors ( $n ) {
+    my %factors;
+    my $output = 0;
+    my $nn     = $n;
+    for my $i ( 2 .. $n - 1 ) {
+        if ( $nn % $i == 0 ) {
+            while ( $nn % $i == 0 ) {
+                $factors{$i}++;
+                $nn /= $i;
+            }
+        }
+    }
+    $output += sum0 map { sum( split //, $_ ) * $factors{$_} } keys %factors;
+    return $output || 0;
+}
+
+sub get_smith_numbers {
+    my @output;
+    my $i = 2;
+    while ( scalar @output < 10 ) {
+        my $d = sum_of_digits($i);
+        my $f = sum_of_factors($i);
+        my $e = $d == $f ? 1 : 0;
+        push @output, $i if $e;
+        exit if $i > 500;
+        $i++;
+    }
+    return @output;
+}