73 lines
1.9 KiB
Python
Executable file
73 lines
1.9 KiB
Python
Executable file
#!/usr/bin/env python
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import enum
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import sys
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from collections.abc import Iterator
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from typing import NamedTuple
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class Point(NamedTuple):
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x: int
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y: int
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class Direction(enum.Enum):
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UP = Point(-1, 0)
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DOWN = Point(1, 0)
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LEFT = Point(0, -1)
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RIGHT = Point(0, 1)
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def apply(self, p: Point) -> Point:
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dx, dy = self.value
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return Point(p.x + dx, p.y + dy)
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def turns(self) -> Iterator["Direction"]:
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match self:
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case Direction.UP | Direction.DOWN:
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turns = (Direction.LEFT, Direction.RIGHT)
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case Direction.LEFT | Direction.RIGHT:
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turns = (Direction.UP, Direction.DOWN)
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yield from turns
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def solve(input: str) -> str:
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def parse(input: str) -> dict[Point, str]:
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return {
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Point(x, y): c
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for x, line in enumerate(input.splitlines())
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for y, c in enumerate(line)
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if c != " "
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}
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def packet_spell(map: dict[Point, str]) -> str:
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letters: list[str] = []
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# Travel starts downward, from outside the map before the first line
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pos = min(map.keys(), key=lambda p: p.x)
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dir = Direction.DOWN
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while True:
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if (letter := map[pos]) not in ("+", "|", "-"):
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letters.append(letter)
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new_dir = dir
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new_pos = dir.apply(pos)
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if new_pos not in map:
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for new_dir in dir.turns():
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if (new_pos := new_dir.apply(pos)) in map:
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break
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else:
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# Must be the end of the line, stop looping
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return "".join(letters)
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dir = new_dir
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pos = new_pos
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map = parse(input)
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return packet_spell(map)
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def main() -> None:
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input = sys.stdin.read()
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print(solve(input))
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if __name__ == "__main__":
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main()
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