Merge pull request #9594 from wlmb/challenges

Add alternative solution

2 files changed, 20 insertions, 1 deletions

diff --git a/challenge-256/wlmb/perl/ch-1.pl b/challenge-256/wlmb/perl/ch-1.pl
index 4163c91776..f5da52e2e6 100755
--- a/challenge-256/wlmb/perl/ch-1.pl
+++ b/challenge-256/wlmb/perl/ch-1.pl
@@ -7,7 +7,7 @@ use v5.36;
 use List::Util qw(sum0);
 die <<~"FIN" unless @ARGV;
     Usage: $0 S1 [S2...]
-    to pair Si with the reverse SJ and count the resulting pairs
+    to pair Si with the reverse Sj and count the resulting pairs
     assuming at most one pair per string.
     FIN
 my %count;
diff --git a/challenge-256/wlmb/perl/ch-1a.pl b/challenge-256/wlmb/perl/ch-1a.pl
new file mode 100755
index 0000000000..8da7ff0e39
--- /dev/null
+++ b/challenge-256/wlmb/perl/ch-1a.pl
@@ -0,0 +1,19 @@
+#!/usr/bin/env perl
+# Perl weekly challenge 256
+# Task 1:  Maximum Pairs
+#
+# See https://wlmb.github.io/2024/02/12/PWC256/#task-1-maximum-pairs
+use v5.36;
+use List::Util qw(sum0);
+die <<~"FIN" unless @ARGV;
+    Usage: $0 S1 [S2...]
+    to pair Si with the reverse Sj and count the resulting pairs
+    FIN
+my %count;
+++$count{$_} for (@ARGV);
+my $result = (sum0 map {
+    my $reverse=reverse $_;
+    my $selfreverse=$_ eq $reverse;
+    $count{$_}*(($count{$reverse}//0)-$selfreverse)
+} keys %count)/2;
+say "@ARGV -> $result";