4 files changed, 60 insertions, 0 deletions
diff --git a/challenge-078/polettix/blog.txt b/challenge-078/polettix/blog.txt
new file mode 100644
index 0000000000..ebf4d89d72
--- /dev/null
+++ b/challenge-078/polettix/blog.txt
@@ -0,0 +1 @@
+https://github.polettix.it/ETOOBUSY/2020/09/18/pwc078-leader-element/
diff --git a/challenge-078/polettix/blog1.txt b/challenge-078/polettix/blog1.txt
new file mode 100644
index 0000000000..fd3ac19e56
--- /dev/null
+++ b/challenge-078/polettix/blog1.txt
@@ -0,0 +1 @@
+https://github.polettix.it/ETOOBUSY/2020/09/19/pwc078-left-rotation/
diff --git a/challenge-078/polettix/perl/ch-1.pl b/challenge-078/polettix/perl/ch-1.pl
new file mode 100644
index 0000000000..eeb3f6d3e8
--- /dev/null
+++ b/challenge-078/polettix/perl/ch-1.pl
@@ -0,0 +1,33 @@
+#!/usr/bin/env perl
+use 5.024;
+use warnings;
+
+# This problem is easier to tackle if moving from the *end* of the array
+# back to the beginning. So, we reverse the input array to analyze it
+# and then reverse it again to get back to the original order.
+sub keep_leaders { # @A <=> @_
+   return (0) unless @_;
+   my $last_leader = $_[-1] - 1;
+   return reverse grep {
+      my $condition = $_ > $last_leader;
+      $last_leader = $_ if $condition;
+      $condition;
+   } reverse @_;
+}
+
+
+# testing stuff
+for my $Aref (
+   [9, 10, 7, 5, 6, 1],
+   [3, 4, 5],
+   [],
+) {
+
+   printout('Input: @A = ', @$Aref);
+   printout('Output: ', keep_leaders(@$Aref));
+}
+
+sub printout {
+   my $prefix = shift;
+   say $prefix, '(', join(', ', @_), ')'
+}
diff --git a/challenge-078/polettix/perl/ch-2.pl b/challenge-078/polettix/perl/ch-2.pl
new file mode 100644
index 0000000000..3328138672
--- /dev/null
+++ b/challenge-078/polettix/perl/ch-2.pl
@@ -0,0 +1,25 @@
+#!/usr/bin/env perl
+use 5.024;
+use warnings;
+use experimental qw< postderef signatures >;
+no warnings qw< experimental::postderef experimental::signatures >;
+
+sub shift_left_by ($n, @A) { (@A[$n..$#A], @A[0..($n-1)]) }
+sub shift_left ($A, $B) { map { [shift_left_by($_, $A->@*)] } $B->@* }
+
+for my $test (
+   [
+      'first test',
+      [qw< 10 20 30 40 50 >],
+      [qw< 3 4 >],
+   ],
+   [
+      'second test',
+      [qw< 7 4 2 6 3 >],
+      [qw< 1 3 4 >]
+   ],
+) {
+   my ($title, $A, $B) = $test->@*;
+   say {*STDERR} $title;
+   say {*STDOUT} '[', join(', ', $_->@*), ']' for shift_left($A, $B);
+}