Day16.py

def one_phase(signal):
	output = []
	for digit in range(len(signal)):
		to_append = 0
		increment = digit+1
		indice = increment-1
		sign = 1
		while indice <= len(signal):
			to_append += sum(signal[indice:indice+increment])*sign
			indice += 2*increment
			sign *= -1
		output.append(abs(to_append)%10)
	return output

def multiple_phases(phases, signal):
	for phase in range(phases):
		signal = one_phase(signal)
		print("Phase {}".format(phase+1))
	return signal

def get_message(phases, puzzle_input):
	# This works if the 'position' is greater than len(puzzle_input)/2
	# Daniel Silverstone gave me the hint for this :)
	position = int(puzzle_input[:7])
	message_relevant_input = [int(digit
		) for digit in puzzle_input][position:][::-1]
	for phase in range(phases):
		running_total = 0
		new_relevant_input = []
		for digit in range(len(message_relevant_input)):
			running_total += message_relevant_input[digit]
			new_relevant_input.append(abs(running_total)%10)
		message_relevant_input = new_relevant_input
		print("Phase {}".format(phase+1))
	return message_relevant_input[::-1][:8]

puzzle_input = "59780176309114213563411626026169666104817684921893071067383638084250265421019328368225128428386936441394524895942728601425760032014955705443784868243628812602566362770025248002047665862182359972049066337062474501456044845186075662674133860649155136761608960499705430799727618774927266451344390608561172248303976122250556049804603801229800955311861516221350410859443914220073199362772401326473021912965036313026340226279842955200981164839607677446008052286512958337184508094828519352406975784409736797004839330203116319228217356639104735058156971535587602857072841795273789293961554043997424706355960679467792876567163751777958148340336385972649515437"

# print(len(puzzle_input))
print("FFT Test output: {}".format(
	multiple_phases(100, [int(digit) for digit in puzzle_input])))
print("Message: {}".format(get_message(100, puzzle_input*10000)))