gistfile1.rb

require 'enumerator'
require 'mu'
def f (ary, size)
  needed = ary.size - size
  while needed > 0 
  result = Array.new
    ary.each_slice(2) do |a,b|
      if needed > 0
        result << a+b
        needed-=1
      else
        result << a << b
      end
    end
    ary = result
  end
  ary
end
a = [1, 15, 5, 11, 8, 8, 3, 13, 7, 9, 10, 6, 4, 12, 14, 2]
t do
  assert_equal f(a,15) , [16, 5, 11, 8, 8, 3, 13, 7, 9, 10, 6, 4, 12, 14,2]
end
t do
  assert_equal f(a,14) , [16, 16, 8, 8, 3, 13, 7, 9, 10, 6, 4, 12, 14,2]
end
t do
  assert_equal f(a,1) , [128]
end