Merge pull request #7094 from wlmb/challenges

Add faster solution

1 files changed, 38 insertions, 0 deletions

diff --git a/challenge-191/wlmb/perl/ch-2c.pl b/challenge-191/wlmb/perl/ch-2c.pl
new file mode 100755
index 0000000000..e212686d6a
--- /dev/null
+++ b/challenge-191/wlmb/perl/ch-2c.pl
@@ -0,0 +1,38 @@
+#!/usr/bin/env perl
+# Perl weekly challenge 191
+# Task 2:  Cute List. Throw duplicates early.
+#
+# See https://wlmb.github.io/2022/11/14/PWC191/#task-2-cute-list
+use v5.36;
+use List::Util qw(all reduce);
+sub cute($n){ # generate all cute sequences of length $n
+    my @sets;
+    for my $position(0..$n-1){
+        for(1..$n){ # Build sets of divisors and multiples of $position+1
+            push @{$sets[$position]}, $_ if ($position+1)%$_==0 || $_%($position+1)==0;
+        }
+    }
+    my $x=reduce {cute_aux($a, $b)} [[]], @sets; # combine sets into cute sequences
+    return $x;
+}
+sub cute_aux($seqs, $nums){ # combine an ongoing set of cute sequences with a set of numbers
+    my @combined =
+        map {
+            my $seq=$_;
+            map {
+                my @seq=@$seq;
+                my @seen;
+                map {$seen[$_]=1} @seq;
+                push @seq, $_;
+                $seen[$_]?():[@seq]
+            } @$nums
+    }
+    @$seqs;
+    [@combined];
+}
+die << "EOF" unless @ARGV;
+Usage: $0 N1 [N2...]
+to count the cute orderings of 1..Ni
+EOF
+die "Only numbers in the range 1..18 are allowed" unless all {1<=$_<=18} @ARGV;
+say "$_ -> ", scalar @{cute($_)} for(@ARGV);