#advent of code 2018 
#day 18
#part 1 and part 2

#at first I thought I can find the loop by simply registering when a value "part2" is repeated once
#(kind of like in an earlier puzzle for that year)
#then I had a correct idea how to find the pattern, 
#but didn't really know how to implement it efficently
#pattern recognition is an implementation of solution provided by Michael Fogleman
#adjusted to my current code
#another issue I had was that I resumed the calculations for part 2 from the state after 10 minutes (part1)
#I needed to save the initial state and then start over
#could probably reduce the code to single loop instead of two separate loops for each part

f = open("input.txt",'r');
Testing = False;
#Testing = True; 
if Testing:
	f.close();
	f = open("testinput.txt",'r');

size = 50;
if Testing: size = 10;

#part 1

CurrentState = {};

for r,l in enumerate(f):
	#print(len(l));
	for c,a in enumerate(l):
		CurrentState.update({(r,c):a});
InitialState = CurrentState.copy();
f.close();

for x in range(size):
	for y in range(size):
		print(CurrentState[(x,y)],end="");
	print();

#check if each adjacent position is still within grid range
def GetAdjacent(Cords):
	Adjacent = [];
	if (Cords[0] -1 >= 0 and Cords[1]-1 >=0):
		Adjacent.append( (Cords[0] -1,Cords[1]-1) );
	if (Cords[0] -1 >= 0):
		Adjacent.append( (Cords[0] -1,Cords[1]) );
	if (Cords[0] -1 >= 0 and Cords[1]+1 < size):
		Adjacent.append( (Cords[0] -1,Cords[1]+1) );
	if (Cords[1]+1 < size):
		Adjacent.append( (Cords[0],Cords[1]+1) );
	if (Cords[1]-1 >= 0):
		Adjacent.append( (Cords[0],Cords[1]-1) );
	if (Cords[0] +1 < size and Cords[1]-1 >=0):
		Adjacent.append( (Cords[0] +1,Cords[1]-1) );
	if (Cords[0] +1 < size):
		Adjacent.append( (Cords[0] +1,Cords[1]) );
	if (Cords[0] +1 < size and Cords[1]+1 < size):
		Adjacent.append( (Cords[0] +1,Cords[1]+1) );
	return Adjacent;
	
def GetAcres(area, adj):
	acres = [];
	for c in adj:
		acres.append(area[c]);
	return acres;

def ChangeState(area, Cords):
	s = area[Cords];
	adj = GetAdjacent(Cords);
	Acres = GetAcres(area, adj);
	if (s == "." and Acres.count("|")>=3):
		s = "|";
	elif (s == "|" and Acres.count("#")>=3):
		s = "#";
	elif (s == "#" and Acres.count("#")>=1 and Acres.count("|")>=1):
		s = "#";
	elif (s == "#"):
		s = ".";
	return s;

SimTime = 10; #minutes

InitialState = CurrentState.copy();
for t in range(SimTime):
	NextState = {};
	for x in range(size):
		for y in range(size):
			NextState.update({(x,y):ChangeState(CurrentState,(x,y))});
	CurrentState = NextState.copy();
	'''
	print("MINUTE ",t);
	for x in range(size):
		for y in range(size):
			print(CurrentState[(x,y)],end="");
		print();
	print();
	'''
summary = list(CurrentState.values());

woods = summary.count("|");
lumbs = summary.count("#");
part1 = woods*lumbs;
print("part 1 = ", part1);

#part 2

SimTime2 = 1000000000; #minutes for part2
values = {};
prev = 0;

CurrentState = InitialState.copy();
for t in range(1,SimTime2):
	NextState = {};
	for x in range(size):
		for y in range(size):
			NextState.update({(x,y):ChangeState(CurrentState,(x,y))});
	CurrentState = NextState.copy();
	summary = list(CurrentState.values());
	woods = summary.count("|");
	lumbs = summary.count("#");
	part2 = woods*lumbs;
	loop = t - values.get(part2,0);
	if (loop == prev):
		if SimTime2%loop == t%loop:
			break;
	values[part2]=t;
	prev = loop;

print("part 2 = ", part2);