From 235a609b1e20d39b4753e7ae015f435c6be40fa8 Mon Sep 17 00:00:00 2001
From: Kjetil S <kjetilskotheim@gmail.com>
Date: Wed, 20 Jul 2022 20:13:33 +0200
Subject: https://theweeklychallenge.org/blog/perl-weekly-challenge-174/

---
 challenge-174/kjetillll/perl/ch-1.pl | 15 +++++++++++++++
 challenge-174/kjetillll/perl/ch-2.pl | 27 +++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 challenge-174/kjetillll/perl/ch-1.pl
 create mode 100644 challenge-174/kjetillll/perl/ch-2.pl

diff --git a/challenge-174/kjetillll/perl/ch-1.pl b/challenge-174/kjetillll/perl/ch-1.pl
new file mode 100644
index 0000000000..0bad1b08f9
--- /dev/null
+++ b/challenge-174/kjetillll/perl/ch-1.pl
@@ -0,0 +1,15 @@
+#!/usr/bin/perl
+use List::Util 'sum'; use v5.10; use strict; use warnings;
+
+my $want = 19;
+my $n = 0;
+
+while( $want > 0 ) {
+
+    my @d = split //, $n;       #array d gets digits
+
+    say $n and $want-- if $n == sum( map $d[$_-1]**$_, 1..@d);
+
+    $n++;
+
+}
diff --git a/challenge-174/kjetillll/perl/ch-2.pl b/challenge-174/kjetillll/perl/ch-2.pl
new file mode 100644
index 0000000000..0a2b91a1b7
--- /dev/null
+++ b/challenge-174/kjetillll/perl/ch-2.pl
@@ -0,0 +1,27 @@
+#!/usr/bin/perl
+use List::MoreUtils 'indexes'; use v5.10; use strict; use warnings;
+
+say permutation2rank( [1,0,2] );
+
+say "[@{[@{rank2permutation( [0,1,2], 1 )}]}]" if $"=',';
+
+sub permutation2rank {
+    indexes {"@$_" eq "@{ $_[0] }"} perms( sort {$a<=>$b} @{ $_[0] } )
+}
+
+sub rank2permutation {
+    ( perms( @{ $_[0] } ) )[pop]
+}
+
+sub perms {
+    my(@i,@r) = 0..$#_;
+    @_ || return;
+    while ( push @r, [@_[@i]] ) {
+	my $p = $#i || last;
+	--$p || last while $i[$p-1] > $i[$p];
+	push @i, reverse splice @i, my$q=$p;
+	++$q while $i[$p-1] > $i[$q];
+	@i[$p-1,$q] = @i[$q,$p-1];
+    }
+    @r
+}
-- 
cgit