class MergeSort

	def mergeSort(list, low, high)
		return if low >= high
		mid = (low+high)/2
		mergeSort(list, low, mid)
		mergeSort(list, mid+1, high)
		merge(list, low, mid, high)
	end

	def merge(list, low, mid, high)
		arr = Array.new(high-low+1)
		i=low
		j=high
		k=0

		while (i<=mid && j<=high) do
			if list[i] < list[j] then
				arr[k] = list[i]
				i+=1	
			else
				arr[k] = list[j]
				j+=1	
			end
			k+=1
			i+=1
			j+=1
		end


		if i<=mid then 
			(list[i..mid]).each do |e|
				arr[k]=e
				k+=1
			end	
		elsif j<=high
			(list[j..high]).each do |e|
				arr[k]=e
				k+=1	
			end
		end
		s=0
		(low..high).each do |e| 
			list[e] = arr[s]
			s+=1
		end
		puts list[low..high] 
	end

end

sort=MergeSort.new
sort.mergeSort([4,3,2,1],0,3)


#Compilation results :=
# MergeSort.rb:21: syntax error, unexpected keyword_else
# MergeSort.rb:24: syntax error, unexpected keyword_end
# MergeSort.rb:28: syntax error, unexpected keyword_end
# MergeSort.rb:35: syntax error, unexpected keyword_elsif
# 		elsif j<=high
# 		     ^
# MergeSort.rb:39: syntax error, unexpected keyword_end
# MergeSort.rb:44: syntax error, unexpected keyword_end
# MergeSort.rb:51: syntax error, unexpected $end, expecting keyword_end
# sort.mergeSort([4,3,2,1],0,3)
#                              ^