#advent of code 2025
#day 07
part1=0;
part2=0;
#parsing
grid=dict();
Ymax=0;
Xmax=0;
PuzzleInput=open("07.in","r");
for y,line in enumerate(PuzzleInput):
	Ymax+=1;
	for x,c in enumerate(line.replace("\n","")):
		grid[(x,y)]=c;
		Xmax=max(Xmax,x+1);
		if c=="S":
			Start=(x,y); 
			grid[(x,y)]=".";
PuzzleInput.close();
#solution
total=(0,0);
pathing=dict();
pathing[total]=set();
hitBottom=dict();
splitters=set(); #encountered splitters
beams=set([(Start,total)]);
#recursive search
def findTimelines(point):
	if point in hitBottom:
		return hitBottom[point];
	hitBottom[point]=0;
	for path in pathing[point]:
		hitBottom[point]+=findTimelines(path);
	return hitBottom[point];

for step in range(0,Ymax+1,2): #every 2nd line is empty so i'm skipping it
	newbeams=set();
	while beams:
		b,prev=beams.pop();
		pathing[prev].add(b);
		if b not in pathing: pathing[b]=set();
		bx,by=b;
		beam=(bx,by+2);
		if grid.get(beam,".")=="^":
			splitters.add(beam);
			newbeams.add(((bx+1,by+2),(bx,by)));
			newbeams.add(((bx-1,by+2),(bx,by)));
		else:
			newbeams.add(((bx,by+2),(bx,by)));
		if by+2>Ymax and b not in hitBottom: 
			hitBottom[b]=1; #register from which points beams hit the bottom
	beams=newbeams;

part1=len(splitters);
part2=findTimelines(Start);
print("part 1",part1,part1==1533);
print("part 2",part2,part2==10733529153890);