Naive merge sort in ruby.

merge_sort.rb

class Array
  def merge_sort
    c = self.count
    return self if c <= 1
    mid = c/2
    left = self[0,mid].merge_sort
    right = self[mid, mid+1].merge_sort

    output = []
    l = 0;
    r = 0;

    while (l < left.count && r < right.count)
      if (left[l] < right[r])
        output << left[l]
        l += 1
      else
        output << right[r]
        r += 1
      end
    end

    output << left[l, left.count-l] 
    output << right[r, right.count-r] 
    output.flatten
  end
end

a = (1..10000).to_a.shuffle

puts "Sorted: #{a.merge_sort}"