Solution to task 1

1 files changed, 60 insertions, 0 deletions

diff --git a/challenge-243/jo-37/perl/ch-1.pl b/challenge-243/jo-37/perl/ch-1.pl
new file mode 100755
index 0000000000..0dc839cd04
--- /dev/null
+++ b/challenge-243/jo-37/perl/ch-1.pl
@@ -0,0 +1,60 @@
+#!/usr/bin/perl -s
+
+use Test2::V0 '!float';
+use PDL;
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [--] [N...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N...
+    list of integers
+
+EOS
+
+
+### Input and Output
+
+say count_reverse_pairs(@ARGV);
+
+
+### Implementation
+
+# Count element pairs where $j > $i and $nums[$i] > 2 * $nums[$j].
+
+sub count_reverse_pairs {
+	my $nums = long @_;
+
+    ((sequence($nums) > sequence(1, $nums->dim(0)))
+        & ($nums->dummy(0) > 2 * $nums))->sum;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is count_reverse_pairs(1, 3, 2, 3, 1), 2, 'example 1';
+        is count_reverse_pairs(2, 4, 3, 5, 1), 3, 'example 2';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is count_reverse_pairs(1, 0, -1), 3, 'zero and negative';
+	}
+
+    done_testing;
+    exit;
+}