add old solutions

1 files changed, 18 insertions, 0 deletions

diff --git a/2.pl b/2.pl
new file mode 100755
index 0000000..6b59aed
--- /dev/null
+++ b/2.pl
@@ -0,0 +1,18 @@
+#!/usr/bin/perl
+use strict;
+use warnings;
+
+my $root5 = sqrt 5;
+my $phi = (1 + $root5)/2;
+
+sub fib { int (($phi**$_[0]-(1-$phi)**$_[0])/$root5 + 0.5) }
+
+my $i = 0;
+my $sum = 0;
+while (1) {
+    $i++;
+    my $n = fib $i;
+    last if $n > 1000000;
+    $sum += $n if $n % 2 == 0;
+}
+print "$sum\n";