Solution to task 1

1 files changed, 66 insertions, 0 deletions

diff --git a/challenge-203/jo-37/perl/ch-1.pl b/challenge-203/jo-37/perl/ch-1.pl
new file mode 100755
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+++ b/challenge-203/jo-37/perl/ch-1.pl
@@ -0,0 +1,66 @@
+#!/usr/bin/perl -s
+
+use v5.22;
+use Test2::V0;
+use Math::Prime::Util qw(forcomb vecsum);
+use experimental 'refaliasing';
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV >= 4;
+usage: $0 [-examples] [-tests] [-verbose] [N1 N2 N3 N4...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N1 N2 N3 N4...
+    list of at least four numbers
+
+EOS
+
+
+### Input and Output
+
+say csq(@ARGV);
+
+
+### Implementation
+
+# Count Special Quadruplets:
+# Loop over k-combinations of n, pick the corresponding values, check
+# for the "special quadruplets" condition and count.
+sub csq {
+    \my @l = \@_;
+	my $cnt;
+    # Perl guarantees left-to-right evaluation of operator arguments, so
+    # "pop" is performed before the slice @l[@_] is taken.
+    forcomb {$cnt += $l[pop] == vecsum @l[@_]} @l, 4;
+    $cnt;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is csq(1,2,3,6), 1, 'example 1';
+        is csq(1,1,1,3,5), 4, 'example 2';
+        is csq(3,3,6,4,5), 0, 'example 3';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is csq(0, 1, 2, 3, 6, 11, 20, 37, 68, 125), 7, 'strict sums';
+	}
+
+    done_testing;
+    exit;
+}