From 71ecb0f7220269142d4274fffd04b40b4d8f7052 Mon Sep 17 00:00:00 2001
From: Mohammad S Anwar <mohammad.anwar@yahoo.com>
Date: Tue, 20 Apr 2021 12:04:46 +0100
Subject: - Added Perl solution to "Four Squares Puzzle" task of week 109.

---
 challenge-109/mohammad-anwar/perl/ch-2.pl | 89 +++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 challenge-109/mohammad-anwar/perl/ch-2.pl

(limited to 'challenge-109')

diff --git a/challenge-109/mohammad-anwar/perl/ch-2.pl b/challenge-109/mohammad-anwar/perl/ch-2.pl
new file mode 100644
index 0000000000..f062d02711
--- /dev/null
+++ b/challenge-109/mohammad-anwar/perl/ch-2.pl
@@ -0,0 +1,89 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+use Test::More;
+use Test::Deep;
+
+is_deeply( solve_puzzle(1,2,3,4,5,6,7),
+           [ [7, 2, 6, 1, 3, 5, 4],
+             [7, 3, 2, 5, 1, 4, 6],
+             [6, 4, 5, 1, 2, 7, 3],
+             [6, 4, 1, 5, 2, 3, 7],
+             [4, 5, 3, 1, 6, 2, 7],
+             [5, 6, 2, 3, 1, 7, 4],
+             [3, 7, 2, 1, 5, 4, 6],
+             [4, 7, 1, 3, 2, 6, 5], ] );
+
+done_testing;
+
+=head1
+
+    For my own sanity:
+
+    Box 1 = a + b
+    Box 2 = b + c + d
+    Box 3 = d + e + f
+    Box 4 = f + g
+
+    For the purpose of the puzzle, the sum of all boxes should
+    be a mulitple of 4.
+
+    Box Sum = (a + b) + (b + c + d) + (d + e + f) + (f + g)
+    => (a + b + c + d + e + f + g) + (b + d + f)
+    => (Num Sum) + (b + d + f)
+
+    Each Box Sum = ( (Num Sum) + (b + d + f) )  / 4
+
+    Now find the different combinations of b, d and f that
+    gives unique a, c, g and e as below:
+
+    a = Each Box Sum - b
+    c = a - d
+    g = Each Box Sum - f
+    e = g - d
+
+=cut
+
+sub solve_puzzle {
+    my @n = @_;
+
+    my $num_sum = 0;
+    $num_sum += $_ for @n;
+
+    my $solutions = [];
+    foreach my $b (@n) {
+        my @may_be_d = grep { $b != $_ } @n;
+        foreach my $d (@may_be_d) {
+            my @may_be_f = grep { $d != $_ } @may_be_d;
+            foreach my $f (@may_be_f) {
+                my $box_sum = $b + $d + $f + $num_sum;
+                next unless ($box_sum % 4 == 0);
+                my $each_box_sum = $box_sum / 4;
+
+                my %rem = map { $_ => 1 } @may_be_f;
+                delete $rem{$f};
+
+                my $a = $each_box_sum - $b;
+                next unless exists $rem{$a};
+                delete $rem{$a};
+
+                my $c = $a - $d;
+                next unless exists $rem{$c};
+                delete $rem{$c};
+
+                my $g = $each_box_sum - $f;
+                next unless exists $rem{$g};
+                delete $rem{$g};
+
+                my $e = $g - $d;
+                next unless exists $rem{$e};
+
+                push @$solutions, [$a, $b, $c, $d, $e, $f, $g];
+            }
+        }
+    }
+
+    return $solutions;
+}
-- 
cgit