100 lines
2.4 KiB
Python
100 lines
2.4 KiB
Python
|
#!/usr/bin/env python
|
||
|
|
|
||
|
|
import enum
|
||
|
|
import sys
|
||
|
|
from typing import NamedTuple
|
||
|
|
|
||
|
|
|
||
|
|
class Point(NamedTuple):
|
||
|
|
x: int
|
||
|
|
y: int
|
||
|
|
|
||
|
|
|
||
|
|
class Direction(enum.StrEnum):
|
||
|
|
UP = "^"
|
||
|
|
RIGHT = ">"
|
||
|
|
DOWN = "v"
|
||
|
|
LEFT = "<"
|
||
|
|
|
||
|
|
def step(self, p: Point) -> Point:
|
||
|
|
dx: int
|
||
|
|
dy: int
|
||
|
|
|
||
|
|
match self:
|
||
|
|
case Direction.UP:
|
||
|
|
dx, dy = -1, 0
|
||
|
|
case Direction.RIGHT:
|
||
|
|
dx, dy = 0, 1
|
||
|
|
case Direction.DOWN:
|
||
|
|
dx, dy = 1, 0
|
||
|
|
case Direction.LEFT:
|
||
|
|
dx, dy = 0, -1
|
||
|
|
|
||
|
|
return Point(p.x + dx, p.y + dy)
|
||
|
|
|
||
|
|
def turn_right(self) -> "Direction":
|
||
|
|
match self:
|
||
|
|
case Direction.UP:
|
||
|
|
return Direction.RIGHT
|
||
|
|
case Direction.RIGHT:
|
||
|
|
return Direction.DOWN
|
||
|
|
case Direction.DOWN:
|
||
|
|
return Direction.LEFT
|
||
|
|
case Direction.LEFT:
|
||
|
|
return Direction.UP
|
||
|
|
|
||
|
|
|
||
|
|
class Guard(NamedTuple):
|
||
|
|
pos: Point
|
||
|
|
dir: Direction
|
||
|
|
|
||
|
|
def patrol_step(self, blockers: set[Point]) -> "Guard":
|
||
|
|
next_step = self.dir.step(self.pos)
|
||
|
|
if next_step not in blockers:
|
||
|
|
return Guard(next_step, self.dir)
|
||
|
|
return Guard(self.pos, self.dir.turn_right())
|
||
|
|
|
||
|
|
|
||
|
|
def solve(input: str) -> int:
|
||
|
|
def parse(input: list[str]) -> tuple[Guard, set[Point]]:
|
||
|
|
guard: Guard | None = None
|
||
|
|
blockers: set[Point] = set()
|
||
|
|
|
||
|
|
for x, line in enumerate(input):
|
||
|
|
for y, c in enumerate(line):
|
||
|
|
if c == ".":
|
||
|
|
continue
|
||
|
|
if c == "#":
|
||
|
|
blockers.add(Point(x, y))
|
||
|
|
continue
|
||
|
|
guard = Guard(Point(x, y), Direction(c))
|
||
|
|
|
||
|
|
assert guard is not None # Sanity check
|
||
|
|
return guard, blockers
|
||
|
|
|
||
|
|
def patrol(guard: Guard, blockers: set[Point], dims: Point) -> int:
|
||
|
|
max_x, max_y = dims
|
||
|
|
positions = {guard.pos}
|
||
|
|
while True:
|
||
|
|
if not (0 <= guard.pos.x < max_x):
|
||
|
|
break
|
||
|
|
if not (0 <= guard.pos.y < max_y):
|
||
|
|
break
|
||
|
|
positions.add(guard.pos)
|
||
|
|
guard = guard.patrol_step(blockers)
|
||
|
|
return len(positions)
|
||
|
|
|
||
|
|
lines = input.splitlines()
|
||
|
|
guard, blockers = parse(lines)
|
||
|
|
max_x, max_y = len(lines), len(lines[0])
|
||
|
|
return patrol(guard, blockers, Point(max_x, max_y))
|
||
|
|
|
||
|
|
|
||
|
|
def main() -> None:
|
||
|
|
input = sys.stdin.read()
|
||
|
|
print(solve(input))
|
||
|
|
|
||
|
|
|
||
|
|
if __name__ == "__main__":
|
||
|
|
main()
|