challenges

commit a17b33e4f7efc2dbba5e0d83a392c1130b146752
parent 05b0faa28b0a33f7b61e6dfa72b557b5c87b2603
Author: Ryan Wolf <rwolf@borderstylo.com>
Date:   Sun, 17 Oct 2010 14:53:28 -0700

completed level2 of greplin

Diffstat:
A
greplin/level2.pl
 | 
37
+++++++++++++++++++++++++++++++++++++

1 file changed, 37 insertions(+), 0 deletions(-)
diff --git a/greplin/level2.pl b/greplin/level2.pl
@@ -0,0 +1,37 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+sub isPrime {
+  my $n = shift;
+  return 0 if ($n % 2 == 0);
+  for (my $i = 3; $i < sqrt($n); $i += 2) {
+    return 0 if ($n % $i == 0);
+  }
+  return 1;
+}
+
+my $nminus2 = 1;
+my $nminus1 = 1;
+my $n = 2;
+
+until ($n > 227000 && isPrime($n)) {
+  $nminus2 = $nminus1;
+  $nminus1 = $n;
+  $n = $nminus2 + $nminus1;
+}
+
+print "X: $n\n";
+
+my $m = $n + 1;
+
+# P + 1 % 2 == 0 for all P > 2
+my $sum = 2;
+for (my $i = 3; $i < sqrt($m); $i += 2) {
+  if ($m % $i == 0 && isPrime($i)) {
+    $sum += $i;
+  }
+}
+
+print "sum: $sum\n";