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Implement 2024 day 16 part 2

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Bert Peters
2024-12-16 18:16:05 +01:00
parent f0556c6afe
commit b23f24c567
1 changed files with 37 additions and 17 deletions
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54
2024/src/aoc/days/day16.py
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@@ -2,7 +2,7 @@ import heapq
import numpy
from . import SeparateRunner
from . import CombinedRunner
TURNS = (
(-1, 1),
@@ -10,9 +10,9 @@ TURNS = (
)
class DayRunner(SeparateRunner):
class DayRunner(CombinedRunner):
@classmethod
def part1(cls, input: str) -> int:
def run_both(cls, input: str) -> tuple[int, int]:
grid = numpy.array([list(line) for line in input.strip().split("\n")])
y, x = numpy.where(grid == "S")
@@ -20,37 +20,57 @@ class DayRunner(SeparateRunner):
todo = [(0, x, y, 1, 0)]
best = {
(x, y, 1, 0): 0,
(x, y, 1, 0): (0, []),
}
def enqueue(dist, x, y, dx, dy):
def enqueue(dist, x, y, dx, dy, cx, cy, cdx, cdy):
if grid[y, x] == "#":
return
if (x, y, dx, dy) not in best or best[x, y, dx, dy] > dist:
best[x, y, dx, dy] = dist
if (x, y, dx, dy) not in best or best[x, y, dx, dy][0] > dist:
best[x, y, dx, dy] = (dist, [(cx, cy, cdx, cdy)])
heapq.heappush(todo, (dist, x, y, dx, dy))
elif best[x, y, dx, dy][0] == dist:
best[x, y, dx, dy][1].append((cx, cy, cdx, cdy))
shortest_dist = None
finishes = set()
while todo:
dist, x, y, dx, dy = heapq.heappop(todo)
if best[x, y, dx, dy] < dist:
if best[x, y, dx, dy][0] < dist:
continue
if grid[y, x] == "E":
return dist
if shortest_dist is not None and shortest_dist < dist:
break
enqueue(dist + 1, x + dx, y + dy, dx, dy)
enqueue(dist + 2001, x - dx, y - dy, dx, dy)
if grid[y, x] == "E":
shortest_dist = dist
finishes.add((x, y, dx, dy))
enqueue(dist + 1, x + dx, y + dy, dx, dy, x, y, dx, dy)
enqueue(dist + 2001, x - dx, y - dy, dx, dy, x, y, dx, dy)
for tx, ty in TURNS:
ndx = dy * ty
ndy = dx * ty
enqueue(dist + 1001, x + ndx, y + ndy, ndx, ndy)
enqueue(dist + 1001, x + ndx, y + ndy, ndx, ndy, x, y, dx, dy)
raise ValueError("Did not find path to exit")
assert shortest_dist is not None, "Should find a path to the exit"
@classmethod
def part2(cls, input: str) -> int:
pass
visited_tiles = {(x, y) for x, y, _, _ in finishes}
todo2 = [f for f in finishes]
visited_states = set(todo2)
while todo2:
state = todo2.pop()
for prev in best[state][1]:
if prev not in visited_states:
visited_states.add(prev)
visited_tiles.add((prev[0], prev[1]))
todo2.append(prev)
return shortest_dist, len(visited_tiles)