From 145c060ad7ea5fa2221caae47382fe1207986add Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Wed, 15 Jun 2022 07:06:08 +0100
Subject: use factor_exp rather than factor as avoids the hash stage

---
 challenge-169/james-smith/perl/ch-2.pl | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/challenge-169/james-smith/perl/ch-2.pl b/challenge-169/james-smith/perl/ch-2.pl
index fd49e07cc0..a694061493 100644
--- a/challenge-169/james-smith/perl/ch-2.pl
+++ b/challenge-169/james-smith/perl/ch-2.pl
@@ -4,23 +4,19 @@ use strict;
 
 use warnings;
 use feature qw(say);
-use Math::Prime::Util qw(factor gcd);
+use Math::Prime::Util qw(factor_exp gcd);
 use Time::HiRes qw(time);
 
 my $time = time;
 open my $fh, '>', 'achilles.txt';
 
-for( my( $n, $c, $MAX ) = ( 2, 0, @ARGV ? $ARGV[0] : 1e2 ); $c<$MAX; $n++ ) {
+for( my( $n, $c, $MAX, @f ) = ( 2, 0, @ARGV ? $ARGV[0] : 1e2 ); $c<$MAX; $n++ ) {
 
   ## Factorise $n into prime factors, and count for each factor...
   ##
   ## e.g. 10800 has factors ( 2, 2, 2, 2, 3, 3, 3, 5, 5 ) or 2^4 3^3 5^2
   ##
-  ## So %factors = ( 2 => 4, 3 => 3, 5 => 2 );
-  ##
-
-  my %factors;
-  $factors{$_}++ for factor $n;
+  ## factor_exp returns a list of tuples - [ prime, exponent ]
 
   ## If any of the values in this hash are 1 then we skip to the next number
   ## as it isn't brilliant..
@@ -35,11 +31,8 @@ for( my( $n, $c, $MAX ) = ( 2, 0, @ARGV ? $ARGV[0] : 1e2 ); $c<$MAX; $n++ ) {
   ## factorisation.
 
   say {$fh} sprintf '%6d: %15d = %s', ++$c, $n,
-      join ' . ',
-      map  { "$_^$factors{$_}" }
-      sort { $a <=> $b }
-      keys  %factors
-    if 1 == gcd grep { $_ < 2 ? next : 1 } values %factors
+      join ' . ', map  { "$_->[0]^$_->[1]" } @f
+    if 1 == gcd map { $_->[1] < 2 ? next : $_->[1] } @f = factor_exp $n;
 
     ## Any of the factors is not squared we try the next number in the loop!
     ## The `next` out of grep jumps to the next loop of the foor loop...
-- 
cgit