def read_input(filename):
    sheet = []
    for line in open(filename).read().splitlines():
        sheet.append(list(line))
    return sheet

# filename = "day07/example_input" # 40
filename = "day07/input" # 1560
sheet = read_input(filename)

for y in range(0,len(sheet)):
    for x in range(0,len(sheet[y])):
        if sheet[y][x] == "S":
            sheet[y][x] = 1
        if sheet[y][x] == "^":
            sheet[y][x] = -1
        if sheet[y][x] == ".":
            sheet[y][x] = 0

# "Cheat alert"; figured this out after algorithm hints on reddit
for y in range(0,len(sheet)-1): # skip last line
    for x in range(0,len(sheet[y])):

        # Path starts with weight one
        # Just add weight to next step
        #   if empty (0), weight stays same
        #   if path is "joined", weights are joined/added

        if sheet[y][x] > 0:
            # Shoot ray down
            if sheet[y+1][x] == -1: # split
                sheet[y+1][x+1] += sheet[y][x]
                sheet[y+1][x-1] += sheet[y][x]
            else:
                sheet[y+1][x] += sheet[y][x]
# Last line of sheet contains the added/joined paths, add them up

paths = 0
for i in sheet[-1]:
    paths += i

print(f"Total number of paths: {paths}")