Solution to task 1

1 files changed, 69 insertions, 0 deletions

diff --git a/challenge-106/jo-37/perl/ch-1.pl b/challenge-106/jo-37/perl/ch-1.pl
new file mode 100755
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+++ b/challenge-106/jo-37/perl/ch-1.pl
@@ -0,0 +1,69 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use List::Util qw(min max);
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [--] [num...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+num...
+    numbers to examine
+
+EOS
+
+
+### Input and Output
+
+say max_gap(@ARGV);
+
+
+### Implementation
+
+# Regardless of the sorting algorithm in use, every pair of neighboring
+# elements must be compared in the process.  Otherwise the succession of
+# such pair would remain undetermined.  Finding the gaps as mimimum
+# differences while comparing and taking the maximum thereof afterwards.
+sub max_gap {
+	my %gap;
+    # Discard the sort result.
+    () = sort {
+        my ($l, $h) = $a < $b ? ($a, $b) : ($b, $a);
+        # Considering different values only.
+        $gap{$l} = min $h - $l,  ($gap{$l} // 'inf') if $h > $l;
+        $a <=> $b} @_;
+
+    (max values %gap) // 0;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+        is max_gap(2, 9, 3, 5), 4, 'example 1';
+        is max_gap(1, 3, 8, 2, 0), 5, 'example 2';
+        is max_gap(5), 0, 'example 3';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+        is max_gap(1, -1, -2, -3, 3, 2, 1, -1), 2, 'non-unique values';
+        is max_gap(0, 0, 0), 0, 'constant value';
+        is max_gap(2, 5), 3, 'pair';
+	}
+
+    done_testing;
+    exit;
+}