Solution to task 1

1 files changed, 67 insertions, 0 deletions

diff --git a/challenge-198/jo-37/perl/ch-1.pl b/challenge-198/jo-37/perl/ch-1.pl
new file mode 100755
index 0000000000..c406cbc810
--- /dev/null
+++ b/challenge-198/jo-37/perl/ch-1.pl
@@ -0,0 +1,67 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+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_max_gap(@ARGV);
+
+
+### Implementation
+
+# Sort the numbers, build pairs of adjacent values, take the differences
+# of the pairs by flipping the sign of the second elements and summing
+# over the pairs.  Then count the elements having the maximum value.
+sub count_max_gap {
+    return 0 unless @_ > 1;
+    my $gap = sumover long(@_)->qsort->lags(0, 1, 2)->xchg(0, 1) * long 1, -1;
+
+    $gap->where($gap == max $gap)->dim(0);
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is count_max_gap(qw(2 5 8 1)), 2, 'example 1';
+        is count_max_gap(3), 0, 'example 2';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is count_max_gap(qw(8 6 4 3 2 1)), 2, 'max count not at max gap';
+        is count_max_gap(qw(3 3 3)), 2, 'zero gap';
+        is count_max_gap(qw(5 3 2 1)), 1, 'single max gap';
+        is count_max_gap(qw(1 2 3 -1)), 1, 'negative number in max gap';
+        is count_max_gap(2, 1), 1, 'single gap';
+        is count_max_gap(), 0, 'empty list';
+	}
+
+    done_testing;
+    exit;
+}