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from collections import defaultdict
from utils import open_day, Point2D, adjacent_bounded
from heapq import heappop, heappush
def a_star(start, goal, neighbours, h, d):
vtoi = dict()
itov = dict()
i = 0
def intern(v):
nonlocal i
ret = vtoi.get(v)
if ret is None:
ret = i
vtoi[v] = i
itov[i] = v
i += 1
return ret
open_set = {start}
open_heapq = [(0, intern(start))]
came_from = dict()
g_score = defaultdict(lambda: float('inf'))
g_score[start] = 0
f_score = defaultdict(lambda: float('inf'))
f_score[start] = h(start)
while open_set:
while True:
f, current = heappop(open_heapq)
current = itov[current]
if current in open_set: break
if current == goal:
return f
open_set.remove(current)
for neighbour in neighbours(current):
tentative_g = g_score[current] + d(current, neighbour)
if tentative_g < g_score[neighbour]:
came_from[neighbour] = current
g_score[neighbour] = tentative_g
f_score[neighbour] = tentative_g + h(neighbour)
open_set.add(neighbour)
heappush(open_heapq, (f_score[neighbour], intern(neighbour)))
return None
with open_day(15) as f:
inp = [[int(c) for c in l.rstrip()] for l in f]
def d(a, b):
add = b.x // len(inp[0]) + b.y // len(inp)
x, y = b.x % len(inp[0]), b.y % len(inp)
return (inp[y][x] + add - 1) % 9 + 1
start = Point2D(0, 0)
goal1 = Point2D(len(inp[0]) - 1, len(inp) - 1)
neighbours1 = lambda p: adjacent_bounded(p, Point2D(len(inp[0]), len(inp)), False)
print(a_star(start, goal1, neighbours1, lambda p: 0, d))
goal2 = Point2D(len(inp[0]) * 5 - 1, len(inp) * 5 - 1)
neighbours2 = lambda p: adjacent_bounded(p, Point2D(len(inp[0]) * 5, len(inp) * 5), False)
print(a_star(start, goal2, neighbours2, lambda p: 0, d))
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