# TODO - Track whether a number is happy globally (memoization)


def is_happy_number(num, previous_numbers=None):
	if previous_numbers is None:
		previous_numbers = []
	previous_numbers.append(num)

	if num == 1:
		return True
	digits = list(str(num))

	happy_exp = 0
	for digit in digits:
		happy_exp += int(digit)**2

	if happy_exp in previous_numbers:
		return False

	return is_happy_number(happy_exp, previous_numbers)