Don't watch my size; I'm dangerous.

1 files changed, 36 insertions, 0 deletions

diff --git a/challenge-052/dave-jacoby/perl/ch-1.pl b/challenge-052/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..4a9b1a5526
--- /dev/null
+++ b/challenge-052/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,36 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say postderef signatures state };
+no warnings qw{ experimental::postderef experimental::signatures };
+
+# A number is called a stepping number if the adjacent digits
+# have a difference of 1. For example, 456 is a stepping number
+# but 129 is not.
+
+if ( scalar @ARGV > 1 ) {
+    my @nums = sort grep { $_ >= 100 && $_ <= 999 } map { int } @ARGV;
+    my @list = get_stepping_numbers( $nums[0], $nums[-1] );
+    say join ", ", @list;
+}
+else {
+    my @list = get_stepping_numbers( 100, 999 );
+    say join ", ", @list;
+}
+
+sub get_stepping_numbers ( $low, $high ) {
+    my @output;
+    for my $n ( $low .. $high ) {
+        my @n = split //, $n;
+        push @output, $n
+            if off_by_one( $n[0], $n[1] ) && off_by_one( $n[1], $n[2] );
+    }
+    return @output;
+}
+
+sub off_by_one ( $i, $j ) {
+    return 1 if $i == $j + 1;
+    return 1 if $i == $j - 1;
+    return 0;
+}