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import sys
sys.path.append("../common")
import aoc
tmap = [list(l) for l in aoc.data.split("\n") if len(l) != 0]
xlen, ylen = len(tmap[0]), len(tmap)
arrows = dict()
arrows["<"] = (-1, 0)
arrows[">"] = (1, 0)
arrows["^"] = (0, -1)
arrows["v"] = (0, 1)
directions = [(-1,0), (0,-1), (1, 0), (0, 1)] # l - u - r - d
def check_pos(x, y):
if x < xlen and x >= 0 and y < ylen and y >= 0:
return tmap[y][x]
return " "
def correct(x, y):
cr = check_pos(x+1, y)
cl = check_pos(x-1, y)
cu = check_pos(x, y-1)
cd = check_pos(x, y+1)
if cr == "|": cr = " "
if cl == "|": cl = " "
if cu == "-": cu = " "
if cd == "-": cd = " "
r = cr != " "
l = cl != " "
u = cu != " "
d = cd != " "
vsum = r + l + u + d
if vsum > 2:
return "+"
# 2 around
if r:
if l:
return "-"
elif u:
return "/"
else:
return "\\"
else:
if not l:
return "|"
elif u:
return "/"
else:
return "\\"
carts = list()
for y in range(ylen):
for x in range(xlen):
if tmap[y][x] in arrows:
carts.append([x, y, arrows[tmap[y][x]], 0, 0])
tmap[y][x] = correct(x,y)
def cart_at(x, y):
global carts
for i in range(len(carts)):
c = carts[i]
if c[0] == x and c[1] == y and not c[4]:
return i
return None
def draw_map():
for y in range(ylen):
f = lambda x : "".join(["#" if cart_at(x,y) != None else tmap[y][x]])
aoc.debug([f(x) for x in range(len(tmap[y]))])
def advance(cart):
ncart = [0 for x in range(5)]
ncart[0] = cart[0]+cart[2][0]
ncart[1] = cart[1]+cart[2][1]
col = cart_at(ncart[0], ncart[1])
if col != None:
return ncart[0], ncart[1], col
c = tmap[ncart[1]][ncart[0]]
d = directions.index(cart[2])
if c == "+":
d = (d + len(directions)-1 + cart[3]) % len(directions)
ncart[2] = directions[d]
ncart[3] = (cart[3] + 1) % 3
else: # dont need to change direction for '-' and '|'
if c == "/":
ncart[2] = directions[3-d]
elif c == "\\":
if d == 0: #l
ncart[2] = directions[1]
elif d == 1: #u
ncart[2] = directions[0]
elif d == 2: #r
ncart[2] = directions[3]
elif d == 3: #d
ncart[2] = directions[2]
else:
ncart[2] = cart[2]
ncart[3] = cart[3]
return ncart
def solve1(args):
global carts
crash = None
while not crash:
carts = sorted(carts, key=lambda x:(x[0], x[1]))
for c in range(len(carts)):
nc = advance(carts[c])
if len(nc) == 3:
crash = nc
break
else:
carts[c] = nc
return f"{crash[0]},{crash[1]}"
def solve2(args):
global carts
while len(carts) > 1:
carts = sorted(carts, key=lambda x:(x[0], x[1]))
rcarts = list()
for c in range(len(carts)):
if carts[c][4]: continue;
nc = advance(carts[c])
if len(nc) == 3:
carts[c][4] = 1
carts[nc[2]][4] = 1
rcarts.append(carts[c])
rcarts.append(carts[nc[2]])
else:
carts[c] = nc
for c in rcarts:
if c in carts: # prevent doubles
carts.remove(c)
return f"{carts[0][0]},{carts[0][1]}"
aoc.run(solve1, solve2)
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