Solution 076 Task 1 Perl LK

1 files changed, 48 insertions, 0 deletions

diff --git a/challenge-076/lubos-kolouch/perl/ch-1.pl b/challenge-076/lubos-kolouch/perl/ch-1.pl
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+#!/usr/bin/perl 
+#===============================================================================
+#
+#         FILE: ch-1.pl
+#
+#        USAGE: ./ch-1.pl  
+#
+#  DESCRIPTION: https://perlweeklychallenge.org/blog/perl-weekly-challenge-076/
+#
+#              Task 1 - Prime Sum
+#
+#       AUTHOR: Lubos Kolouch
+#===============================================================================
+
+use strict;
+use warnings;
+use Math::Prime::Util qw/is_prime/;
+
+sub get_nr_primes {
+    my $what = shift;
+
+    # if the number is prime, we need just 1 number to represent it
+
+    return 1 if is_prime($what);
+
+    # if the number is even, we need 2 primes thanks to Goldbach's conjecture
+    return 2 if $what % 2 == 1;
+
+    # if the number - 2 is prime, return 2
+    return 2 if is_prime($what - 2);
+
+    # if the number -3 is prime, return 2 (3 and the prime)
+    return 2 if is_prime($what - 3);
+
+    # otherwise return 3 - it is 3 and 2 primes forming $what - 3 thanks to
+    # Goldbach's conjecture
+    
+    return 3
+}
+
+
+use Test::More;
+
+is(get_nr_primes(9), 2, 'test 9');
+is(get_nr_primes(10), 2, 'test 10');
+is(get_nr_primes(2), 1, 'test 2');
+
+done_testing;