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2022/day12.py

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2022-12-24 14:59:27 +00:00
import fileinput
from collections import deque
map = []
start_pos = None
end_pos = None
for y, row in enumerate(fileinput.input(mode="rb")):
row = row.strip()
if not row:
continue
r = []
for x, col in enumerate(row):
match col:
case 83:
start_pos = (x, y)
r.append(0)
case 69:
end_pos = (x, y)
r.append(25)
case _:
r.append(col - 97)
map.append(r)
assert start_pos is not None
assert end_pos is not None
part1, part2 = None, None
trace: tuple[tuple[int, int], ...] = ()
stack = deque([(0, end_pos, trace)])
visited = set()
while stack:
h_, (x, y), trace = stack.popleft()
if x < 0 or x >= len(map[0]) or y < 0 or y >= len(map) or (x, y) in visited:
continue
h = map[y][x]
if h - h_ < -1:
continue
if part1 is None and (x, y) == start_pos:
part1 = len(trace)
if part2 is None and h == 0:
part2 = len(trace)
if part1 is not None and part2 is not None:
break
visited.add((x, y))
trace = trace + ((x, y, h),)
stack.append((h, (x - 1, y + 0), trace))
stack.append((h, (x + 1, y + 0), trace))
stack.append((h, (x + 0, y - 1), trace))
stack.append((h, (x + 0, y + 1), trace))
else:
assert False
print(part1, part2)