Just finished up Problem #13. Straight up brute force ran really well, but I figured I could save some cycles by only adding up the last 11 digits.

I ran this and #25 through ruby 1.8.6 and 1.9.1 and was suprised to see that it ran much slower in the newer version. Everything else I’ve tried has run much better.

Here are some numbers I found to be pretty indicative. Bummer.

$ time ruby 13.rb

real	0m0.009s
user	0m0.008s
sys	0m0.000s

$ time ruby1.9 13.rb

real	0m0.026s
user	0m0.020s
sys	0m0.004s

Problem 13

Work out the first ten digits of the sum of the following one-hundred 50-digit numbers.

input = File.new("files/13.txt", "r")
total = 0

input.each do |i|
  total += i.slice(0..10).to_i
end

puts total.to_s.slice(0,10)