exercism-perl5

commit a51078da241dce34a49be3de9f87c0c7e4856240
parent 70d183143d2656c2874489a5eac500cf969b064e
Author: Samir Parikh <noreply@samirparikh.com>
Date:   Thu, 26 May 2022 13:18:25 +0000

get all tests to pass

Diffstat:
M
sieve/Sieve.pm
 | 
23
++++++++++++++++++++++-

1 file changed, 22 insertions(+), 1 deletion(-)
diff --git a/sieve/Sieve.pm b/sieve/Sieve.pm
@@ -4,9 +4,30 @@ use warnings;
 use Exporter qw<import>;
 our @EXPORT_OK = qw<find_primes>;
 
+#use Data::Dumper;
+
 sub find_primes {
   my ($limit) = @_;
-  return undef;
+  return [ ]   if ( $limit == 1 ); # no primes under 2
+  return [ 2 ] if ( $limit == 2);
+
+  # initialize our sieve as a hash with a default value of `1`, assuming
+  # for now that all numbers within the range are prime
+  my %sieve = map { $_ => 1 } ( 2 .. $limit );
+
+  foreach my $candidate ( 2 .. $limit ) {
+    my $multiple = $candidate * 2; # start at next multiple
+    while ( $multiple <= $limit ) {
+      $sieve{ $multiple } = 0;
+      $multiple += $candidate;
+    }
+  }
+
+  # store in array @primes all keys of `%sieve` where $sieve{ $_ } is
+  # still equal to 1, indicating that the key is a prime number
+  my @primes = sort { $a <=> $b } grep{ $sieve{ $_ } } keys %sieve;
+
+  return \@primes;
 }
 
 1;