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#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);
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