わかる

mergesort.rb

class Array
	def merge(arr)
		org = self.reverse
		arr = arr.reverse
		new = []
		loop{
			if org == []
				return new.concat(arr.reverse)
			end
			if arr == []
				return new.concat(org.reverse)
			end
			if org.last < arr.last
				new << org.pop
			else
				new << arr.pop
			end
		}
		new
	end

	def merge_sort
		a = self.map{|e|[e]}
		while a.size != 1 do
			a = a.each_slice(2).map{|a|a.size == 1 ? a[0] : a[0].merge(a[1])}
		end
		a[0]
	end
end