66 lines
1.6 KiB
Python
66 lines
1.6 KiB
Python
|
#!/usr/bin/env python
|
||
|
|
|
||
|
|
import heapq
|
||
|
|
import sys
|
||
|
|
from typing import Iterator, NamedTuple
|
||
|
|
|
||
|
|
|
||
|
|
class Point(NamedTuple):
|
||
|
|
x: int
|
||
|
|
y: int
|
||
|
|
|
||
|
|
def neighbours(self) -> Iterator["Point"]:
|
||
|
|
for dx, dy in (
|
||
|
|
(-1, 0),
|
||
|
|
(1, 0),
|
||
|
|
(0, -1),
|
||
|
|
(0, 1),
|
||
|
|
):
|
||
|
|
yield Point(self.x + dx, self.y + dy)
|
||
|
|
|
||
|
|
|
||
|
|
DIMS = Point(70, 70)
|
||
|
|
|
||
|
|
|
||
|
|
def solve(input: str) -> int:
|
||
|
|
def parse(input: list[str]) -> list[Point]:
|
||
|
|
return [Point(*map(int, line.split(","))) for line in input]
|
||
|
|
|
||
|
|
def djikstra(start: Point, end: Point, blocks: set[Point]) -> int:
|
||
|
|
# Priority queue of (distance, point)
|
||
|
|
queue = [(0, start)]
|
||
|
|
seen: set[Point] = set()
|
||
|
|
|
||
|
|
while len(queue) > 0:
|
||
|
|
cost, p = heapq.heappop(queue)
|
||
|
|
if p == end:
|
||
|
|
return cost
|
||
|
|
# We must have seen p with a smaller distance before
|
||
|
|
if p in seen:
|
||
|
|
continue
|
||
|
|
# First time encountering p, must be the smallest distance to it
|
||
|
|
seen.add(p)
|
||
|
|
# Add all neighbours to be visited
|
||
|
|
for n in p.neighbours():
|
||
|
|
if p in blocks:
|
||
|
|
continue
|
||
|
|
if not 0 <= p.x <= DIMS.x:
|
||
|
|
continue
|
||
|
|
if not 0 <= p.y <= DIMS.y:
|
||
|
|
continue
|
||
|
|
heapq.heappush(queue, (cost + 1, n))
|
||
|
|
|
||
|
|
assert False # Sanity check
|
||
|
|
|
||
|
|
coords = parse(input.splitlines())
|
||
|
|
return djikstra(Point(0, 0), DIMS, set(coords[:1024]))
|
||
|
|
|
||
|
|
|
||
|
|
def main() -> None:
|
||
|
|
input = sys.stdin.read()
|
||
|
|
print(solve(input))
|
||
|
|
|
||
|
|
|
||
|
|
if __name__ == "__main__":
|
||
|
|
main()
|