From 15fcbedb28557e5afbb44a6c8404f65b84c9f61c Mon Sep 17 00:00:00 2001
From: CY Fung <fungcheokyin@gmail.com>
Date: Sun, 18 Jun 2023 21:17:25 +0800
Subject: Week 221 Task 2

---
 challenge-221/cheok-yin-fung/perl/ch-2.pl | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 challenge-221/cheok-yin-fung/perl/ch-2.pl

diff --git a/challenge-221/cheok-yin-fung/perl/ch-2.pl b/challenge-221/cheok-yin-fung/perl/ch-2.pl
new file mode 100644
index 0000000000..99c91e8982
--- /dev/null
+++ b/challenge-221/cheok-yin-fung/perl/ch-2.pl
@@ -0,0 +1,27 @@
+# The Weekly Challenge 221
+# Task 2 Arithmetic Subsequence
+# Brute-force approach, just hope the number of lines is minimalist
+use v5.30.0;
+use warnings;
+use List::Util qw/all sum uniqint/;
+use List::MoreUtils qw/slide/;
+
+sub as {
+    my @arr = @_;
+    return 1 if scalar @arr == 1;
+    my $len_of_longest_as = 2;
+    for my $i (reverse 7..2**($#arr+1)-1) {
+        my $l = length sprintf("%0b", $i);
+        my @bin = split "", "0" x ($#arr+1-$l).sprintf("%0b", $i);
+        next if sum (@bin) < $len_of_longest_as;
+        my @n_arr = map {$arr[$_]} grep {$bin[$_]} (0..$#arr);
+        my @diffs = slide {$a-$b} @n_arr;
+        $len_of_longest_as = sum (@bin) if scalar (uniqint @diffs) == 1;
+    }
+    return $len_of_longest_as;
+}
+
+use Test::More tests=> 3;
+ok as(9, 4, 7, 2, 10) == 3;
+ok as(3, 6, 9, 12) == 4;
+ok as(20, 1, 15, 3, 10, 5, 8) == 4;
-- 
cgit