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L = {
(i, j): c
for (i, l) in enumerate(open("input").readlines())
for (j, c) in enumerate(l.strip())
}
W = max(j for (i, j) in L.keys()) + 1
C = W // 2
# from day 9
def predict(s):
f = []
while s:
f.append(s[-1])
s = [s[i] - s[i - 1] for i in range(1, len(s))]
return sum(f)
# more efficient than predict
from numpy.polynomial import Polynomial
FIN = 26501365
PREHEAT = 5
LIM1 = 64
LIM2 = C + PREHEAT * W
pre = {-1: 0}
s = [(i, j) for (i, j) in L if L[(i, j)] == "S"][0]
q = [(s, 0)]
v = set()
part1 = 0
while q:
p, n = q.pop(0)
if n == LIM1 and not part1:
part1 = pre[LIM1 - 1]
if n == LIM2:
break
for move in [(0, 1), (1, 0), (0, -1), (-1, 0)]:
np = (p[0] + move[0], p[1] + move[1])
_np = (np[0] % W, np[1] % W)
if _np not in L or np in v or L[_np] == "#":
continue
q.append((np, n + 1))
v.add(np)
if n % 2:
if n not in pre:
pre[n] = pre[n - 2]
pre[n] += 1
print(part1)
poly = {}
for i, p in pre.items():
if (i + 1) % W == C:
poly[i + 1] = p
f = Polynomial.fit(list(poly.keys()), list(poly.values()), 2)
res = f(FIN)
print(f, round(res))
# for i in range(PREHEAT, (FIN - C) / W + 1):
# poly.append(predict(poly))
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