Add solution fo challenge-147 task 1

1 files changed, 47 insertions, 0 deletions

diff --git a/challenge-147/alexander-pankoff/perl/ch-1.pl b/challenge-147/alexander-pankoff/perl/ch-1.pl
new file mode 100644
index 0000000000..fe0009ac63
--- /dev/null
+++ b/challenge-147/alexander-pankoff/perl/ch-1.pl
@@ -0,0 +1,47 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+use feature qw'say signatures';
+no warnings qw'experimental::signatures';
+
+use Data::Dumper;
+use List::Util qw(all);
+
+run() unless caller();
+
+sub run() {
+    say join( ", ", left_truncatable_primes(20) );
+}
+
+sub left_truncatable_primes($n) {
+
+    my @primes = ();
+    for ( my $i = 2 ; @primes <= $n ; $i++ ) {
+        push @primes, $i if is_left_truncatable_prime($i);
+
+    }
+
+    return @primes;
+}
+
+sub is_left_truncatable_prime($x) {
+    return 0 if $x =~ /0/;
+    return 0 if !is_prime($x);
+    return 1 if length $x == 1;
+
+    return is_left_truncatable_prime( substr( $x, 1 ) );
+
+}
+
+sub is_prime($x) {
+
+    return 0 if $x < 2;
+    return 1 if $x < 4;
+
+    for ( my $i = 2 ; $i <= sqrt($x) ; $i++ ) {
+        return 0 if $x % $i == 0;
+    }
+
+    return 1;
+
+}