exercism-perl5

commit 235cd60653aa9e8088ea381afcabfc6703d1ceaf
parent e35bd4e67fe0806a2df1de17c73e968070fc6897
Author: Samir Parikh <noreply@samirparikh.com>
Date:   Fri, 26 Aug 2022 22:29:44 +0000

get all tests to pass

Diffstat:
M
luhn/Luhn.pm
 | 
39
+++++++++++++++++++++++++++++++++------

1 file changed, 33 insertions(+), 6 deletions(-)
diff --git a/luhn/Luhn.pm b/luhn/Luhn.pm
@@ -7,24 +7,51 @@ use feature qw<say>;
 use Exporter qw<import>;
 our @EXPORT_OK = qw<is_luhn_valid>;
 
+use List::Util qw(sum);
+
+sub step1 {
+    my ( $digit ) = @_;
+    if ( $digit * 2 > 9 ) {
+        return $digit * 2 - 9;
+    } else {
+        return $digit * 2;
+    }
+}
+
 sub is_luhn_valid {
     my ($input) = @_;
-    #print "input was originally '$input'\n";
-    $input =~ s/\s+//g; # remove whitespace
-    #print "input = $input\n";
+
+    # remove whitespace
+    $input =~ s/\s+//g;
 
     # return false if string is less than 2 digits
     return 0 if ( length $input < 2 );
 
     # return false if we find a non-decimal character
     return 0 if ( $input =~ m/\D/ );
-    my @numbers = ( $input =~ m/\d/g ); # split out input into array
-    print join( ":", @numbers), "\n";
+
+    # split input into array
+    my @numbers = ( $input =~ m/\d/g );
 
     # the special variable $#numbers represents the index of the last element
     # of the array @numbers
 
-    return undef;
+    if ( $#numbers % 2 ) { # even number of digits, e.g. 1234
+        for ( my $i = 0; $i < $#numbers; $i += 2 ) {
+            $numbers[$i] = step1( $numbers[$i] );
+        }
+    } else { # odd number of digits, e.g. 123
+        for ( my $i = 1; $i < $#numbers; $i += 2 ) {
+            $numbers[$i] = step1( $numbers[$i] );
+        }
+    }
+
+    # fancy way of saying that if the sum of the numbers in the array is NOT
+    # divisible by zero (in which case `sum( @numbers ) % 10` returns a non
+    # zero number which evaluates to true) we return false (0).  Otherwise,
+    # return true (1).
+    return sum( @numbers ) % 10 ? 0 : 1;
+
 }
 
 1;