w288 - Task 1

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+#!/bin/perl
+
+=pod
+
+L<https://theweeklychallenge.org/blog/perl-weekly-challenge-288#TASK1>
+
+Author: Niels 'PerlBoy' van Dijke
+
+Task 1: Closest Palindrome
+Submitted by: Mohammad Sajid Anwar
+
+You are given a string, $str, which is an integer.
+
+Write a script to find out the closest palindrome, not including itself.
+If there are more than one then return the smallest.
+
+|| The closest is defined as the absolute difference minimized between two integers.
+
+=cut
+
+use v5.32;
+use feature qw(signatures);
+no warnings qw(experimental::signatures);
+use common::sense;
+
+use Test2::V0 qw(-no_srand);
+
+use List::Util qw(min);
+
+sub closestPalindrome ($int) {
+  my @p = ($int-1,$int+1); my @d = (-1,+1);
+
+  for (0,1) {
+    $p[$_] += $d[$_] while ($p[$_] > 0 and $p[$_] ne reverse $p[$_]);
+  }
+
+  my $minDelta = min map { abs($int-$_) } @p;
+
+  return [@p[grep { $p[$_] - $d[$_] * $minDelta == $int } (0,1)]];
+}
+
+is(closestPalindrome(123),[121]);
+is(closestPalindrome(2),[1,3]);
+is(closestPalindrome(1400),[1441]);
+is(closestPalindrome(1001),[999]);
+
+done_testing;