from collections import deque



def mergesort(iterable):
	if(len(iterable) == 1):
		return iterable
	
	mid = len(iterable) // 2
	left = mergesort(iterable[:mid])
	right = mergesort(iterable[mid:])

	result = deque()
	while(left or right):
		if(left):
			cmp_left = left[0]
		else:
			cmp_left = None
		if(right):
			cmp_right = right[0]
		else:
			cmp_right = None

		if(cmp_left != None
			and cmp_right != None):
			if(cmp_left < cmp_right):
				result.append(left.pop(0))
			else:
				result.append(right.pop(0))
			continue
		if(cmp_left != None):
			result.append(left.pop(0))
			continue
		if(cmp_right != None):
			result.append(right.pop(0))
			continue
	return list(result)

if( __name__ == "__main__"):
	
	test_data = [0, 1, 4, 5, 2, 9, 12, 3]

	assert mergesort(test_data) == list(sorted(test_data))
	print(mergesort([ 5 , 4 , 21 , 11 , 1 , 17 , 20 , 2 , 3 , 7 , 8 , 22 , 6 , 
			10 , 13 , 14 , 18 , 15 , 16 , 19 , 12 , 9 , 0 ]))