Add Perl solution to challenge 221 task 2

2 files changed, 84 insertions, 0 deletions

diff --git a/challenge-221/paulo-custodio/perl/ch-2.pl b/challenge-221/paulo-custodio/perl/ch-2.pl
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+++ b/challenge-221/paulo-custodio/perl/ch-2.pl
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+#!/usr/bin/env perl
+
+# Challenge 221
+#
+# Task 2: Arithmetic Subsequence
+# Submitted by: Mohammad S Anwar
+# You are given an array of integers, @ints.
+#
+# Write a script to find the length of the longest Arithmetic Subsequence in
+# the given array.
+#
+#
+# A subsequence is an array that can be derived from another array by deleting
+# some or none elements without changing the order of the remaining elements.
+#
+# A subsquence is arithmetic if ints[i + 1] - ints[i] are all the same value
+# (for 0 <= i < ints.length - 1).
+#
+#
+# Example 1:
+# Input: @ints = (9, 4, 7, 2, 10)
+# Output: 3
+#
+# The longest Arithmetic Subsequence (4, 7, 10) can be derived by deleting
+# 9 and 2.
+# Example 2:
+# Input: @ints = (3, 6, 9, 12)
+# Output: 4
+#
+# No need to remove any elements, it is already an Arithmetic Subsequence.
+# Example 3:
+# Input: @ints = (20, 1, 15, 3, 10, 5, 8)
+# Output: 4
+#
+# The longest Arithmetic Subsequence (20, 15, 10, 5) can be derived by deleting
+# 1, 3 and 8.
+
+use Modern::Perl;
+use List::Util 'max';
+
+my @ints = @ARGV;
+my $max_sequence = 0;
+for my $i (0 .. $#ints-1) {
+    for my $j ($i+1 .. $#ints) {
+        my $sequence = find_sequence($ints[$i], @ints[$j .. $#ints]);
+        $max_sequence = max($max_sequence, $sequence);
+    }
+}
+say $max_sequence;
+
+sub find_sequence {
+    my(@ints) = @_;
+    @ints >= 2 or die;
+    my $cur = shift @ints;
+    my $delta = $ints[0] - $cur;
+    my $sequence = 1;
+    while (@ints) {
+        my $next = $cur+$delta;
+        while (@ints && $ints[0] != $next) {
+            shift @ints;
+        }
+        if (@ints) {
+            $cur += $delta;
+            shift @ints;
+            $sequence++;
+        }
+    }
+    return $sequence;
+}
diff --git a/challenge-221/paulo-custodio/t/test-2.yaml b/challenge-221/paulo-custodio/t/test-2.yaml
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+++ b/challenge-221/paulo-custodio/t/test-2.yaml
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+- setup:
+  cleanup:
+  args:     9 4 7 2 10
+  input:
+  output:   3
+- setup:
+  cleanup:
+  args:     3 6 9 12
+  input:
+  output:   4
+- setup:
+  cleanup:
+  args:     20 1 15 3 10 5 8
+  input:
+  output:   4