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L = {
(y, x): c
for y, l in enumerate(open("input").readlines())
for x, c in enumerate(l.strip())
}
W = max(x for (_, x) in L.keys())
H = max(y for (y, _) in L.keys())
def oob(y, x, d):
return x > W or x < 0 or y > H or y < 0
def next(y, x, d):
if d == 0:
return (y - 1, x, d)
if d == 1:
return (y, x + 1, d)
if d == 2:
return (y + 1, x, d)
if d == 3:
return (y, x - 1, d)
def neighbours(y, x, d):
ch = L[(y, x)]
# rule 1
if ch == ".":
return [next(y, x, d)]
# rule 2
if ch == "/":
r = [1, 0, 3, 2]
return [next(y, x, r[d])]
if ch == "\\":
r = [3, 2, 1, 0]
return [next(y, x, r[d])]
# rule 3
if ch == "|" and d in [1, 3]:
return [(y - 1, x, 0), (y + 1, x, 2)]
if ch == "-" and d in [0, 2]:
return [(y, x + 1, 1), (y, x - 1, 3)]
# rule 4
if ch == "|" and d in [0, 2] or ch == "-" and d in [1, 3]:
return [next(y, x, d)]
def visited(sy, sx, sd):
q = [(sy, sx, sd)]
v = set()
v.add(q[0])
while q:
y, x, d = q.pop(0)
ns = neighbours(y, x, d)
for n in ns:
if n not in v and not oob(*n):
v.add(n)
q.append(n)
return len(set((y, x) for (y, x, _) in v))
def solve1():
print(visited(0, 0, 1))
def solve2():
res = 0
for x in range(W):
res = max(res, visited(0, x, 2), visited(H, x, 0))
for y in range(H):
res = max(res, visited(y, 0, 1), visited(y, W, 3))
print(res)
solve1()
solve2()
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