From 87a49e0dde51ea6a342eaecef8820bf0b3bc5ead Mon Sep 17 00:00:00 2001
From: CY Fung <fungcheokyin@gmail.com>
Date: Sun, 12 Jun 2022 06:10:22 +0800
Subject: finalize Task 1

---
 challenge-168/cheok-yin-fung/perl/ch-2.pl | 46 +++++++++++++------------------
 1 file changed, 19 insertions(+), 27 deletions(-)

diff --git a/challenge-168/cheok-yin-fung/perl/ch-2.pl b/challenge-168/cheok-yin-fung/perl/ch-2.pl
index 0f08ab3dc4..3e16406fbd 100644
--- a/challenge-168/cheok-yin-fung/perl/ch-2.pl
+++ b/challenge-168/cheok-yin-fung/perl/ch-2.pl
@@ -1,5 +1,3 @@
-# CAN BE IMPROVED
-
 #!/usr/bin/perl
 # The Weekly Challenge 168
 # Task 2 Home Prime 
@@ -7,14 +5,10 @@
 use v5.24.0;
 use warnings;
 use List::Util qw/reduce/;
-use Math::BigInt::GMP;          # [remark]
-use Math::BigInt::Pari;         # [remark]
-use Math::Prime::Util::GMP qw/is_prime next_prime/;
-use bigint try => 'GMP,Pari';   # [remark]
-# remark: follow suggestions on POD of Math::Prime::Util
-
+use Math::Prime::Util qw/is_prime next_prime/;
+use Math::BigInt;
 
-say hp($ARGV[0]) if defined($ARGV[0]);
+say hp($ARGV[0]) if defined($ARGV[0]) && $ARGV[0] != 1;
 
 
 
@@ -27,8 +21,14 @@ sub hp {
 sub my_hp {
     my $recur_depth = $_[1];
 
+    die "Number involed too large.\n" 
+        if  
+            Math::BigInt->new(18446744073709551616) # 2**64
+                        ->bcmp( Math::BigInt->new($_[0]) )
+              == -1;
+
     die "Walk so far but still cannot get result. :(\n" if $recur_depth > 20;
-    my $num = Math::BigInt->new($_[0]);
+    my $num = $_[0];
     if (is_prime($num) == 2) {
         return $num;
     }
@@ -36,27 +36,23 @@ sub my_hp {
     my @factors = ();
     my $p = 2;
     while ($num != 1) {
-        my $temp_num = $num;
-        if ( $num->bmod($p) == 0 ) {
-            say $p;
+        if (!($num % $p)) {
             push @factors, $p;
-            $num = $num->bdiv($p);
+            $num /= $p;
         }
         else {
             $p = next_prime($p);
         }
-        if ($p > $temp_num->bsqrt()) {
+        if ($p > sqrt $num) {
             push @factors, $num;
             last;
         }
     }
-    my $nxt = join "", @factors;
+    my $nxt = (reduce { $a . $b } @factors);
     say "  $nxt";
     return my_hp($nxt, ++$recur_depth);
 }
 
-
-=pod
 use Test::More tests => 8;
 # test data from OEIS
 ok hp(10) == 773;
@@ -65,16 +61,12 @@ ok hp(32) == 241_271;
 ok hp(40) == 3314192745739;  
 ok hp(44) == 22815088913;  
 ok hp(45) == 3_411_949;
+
+# bigger cases;
 ok hp( 8) == 3331113965338635107;
-ok hp(48) == 6161791591356884791277;
+ok hp(20) == 3318308475676071413;
 
-# time without the last hp(48) test case:
-# real	0m1.963s
-# user	0m1.946s
+# real	0m5.553s
+# user	0m5.535s
 # sys	0m0.016s
-#
-# time without the last hp(48) test case and use simply Math::Prime::Util :
-# real	0m0.133s
-# user	0m0.115s
-# sys	0m0.011s
 
-- 
cgit