From e37393936e2980c429ad282af9fd021ea27f27fe Mon Sep 17 00:00:00 2001
From: Jörg Sommrey <28217714+jo-37@users.noreply.github.com>
Date: Tue, 23 Feb 2021 21:38:45 +0100
Subject: Solution to task 1

---
 challenge-101/jo-37/perl/ch-1.pl | 112 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100755 challenge-101/jo-37/perl/ch-1.pl

diff --git a/challenge-101/jo-37/perl/ch-1.pl b/challenge-101/jo-37/perl/ch-1.pl
new file mode 100755
index 0000000000..22516331d2
--- /dev/null
+++ b/challenge-101/jo-37/perl/ch-1.pl
@@ -0,0 +1,112 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use PDL;
+use Test2::V0 '!float';
+use Math::Prime::Util 'divisors';
+use experimental qw(signatures postderef);
+
+our ($tests, $examples, $verbose, $alt);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [-verbose] [-alt] [n1 n2 ...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+-verbose
+    enable trace output
+
+-alt
+    produce an alternative solution for non-square matrices
+
+n1 n2 ...
+    numbers to roll into a matrix
+
+EOS
+
+
+### Input and Output
+
+say scalar roll(\@ARGV, $alt);
+
+
+### Implementation
+
+# Get matrix form: minimum difference between number of rows and
+# columns.
+sub form :prototype($) ($n) {
+    my @d = divisors $n;
+
+    # Difference of the "middle" divisors.
+    $d[@d / 2] - $d[-(@d / 2 + 1)];
+}
+
+# Roll a matrix from an array of numeric values.
+sub roll ($arr, $alt=0) {
+
+    # Create the starting matrix as a single row or column from a piece
+    # off the list tail, sized according to the matrix' form.  The
+    # solution's orientation is predefined by the starting matrix.
+    # Providing either variants.
+    my $roll = pdl(splice @$arr, -(form(@$arr) + 1))
+        ->slice($alt ? '*,-1:0' : 'X,*')->sever;
+    say $roll if $verbose;
+
+    while (@$arr) {
+        # Left-rotate the current matrix and add an apt piece off the
+        # list tail.
+        $roll = $roll
+            ->slice('-1:0')->xchg(0,1)
+            ->glue(1, pdl splice @$arr, -$roll->dim(1))
+            ->sever;
+        say $roll if $verbose;
+    }
+
+    # Return the solution as an AoA or as the piddle itself depending on
+    # the context.
+    wantarray ? $roll->unpdl->@* : $roll;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    local $alt;
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is [roll [1 .. 4]], [[4, 3], [1, 2]], 'example 1';
+        is [roll [1 .. 6]], [[6, 5, 4], [1, 2, 3]], 'example 2a';
+        is [roll [1 .. 6], 1], [[5, 4], [6, 3], [1, 2]], 'example 2b';
+        is [roll [1 .. 12]],
+            [[9, 8, 7, 6], [10, 11, 12, 5], [1, 2, 3, 4]],
+            'example 3a';
+        is [roll [1 .. 12], 1],
+            [[8, 7, 6], [9, 12, 5], [10, 11, 4], [1, 2, 3]],
+            'example 3b';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is form(12 * 12), 0, 'form 0';
+        is form(11 * 12), 1, 'form 1';
+        is form(12 * 14), 2, 'form 2';
+        is form(9 * 12), 3, 'form 3';
+        is form(137), 136, 'form prime - 1';
+
+        is [roll [1 .. 3]], [[1 .. 3]], 'prime';
+        is [roll [1 .. 3], 1], [[3], [2], [1]], 'alt prime';
+        is [roll [1 .. 9]], [[7, 6, 5], [8, 9, 4], [1, 2, 3]], 'odd size';
+        is [roll [1]], [[1]], 'single element';
+	}
+
+    done_testing;
+    exit;
+}
-- 
cgit