54 lines
1.4 KiB
Python
Executable file
54 lines
1.4 KiB
Python
Executable file
#!/usr/bin/env python
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import sys
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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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def solve(input: list[str]) -> int:
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def parse(input: list[str]) -> tuple[Point, set[Point]]:
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start: Point | None = None
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splitters: set[Point] = set()
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for x, line in enumerate(input):
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for y, c in enumerate(line):
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pos = Point(x, y)
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if c == "S":
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start = pos
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elif c == "^":
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splitters.add(pos)
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assert start is not None
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return start, splitters
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def run_manifold(start: Point, splitters: set[Point]) -> set[Point]:
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beams = {start}
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current_row = {start.y}
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for x in range(start.x + 1, max(p.x for p in splitters) + 1):
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next_row: set[int] = set()
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for y in current_row:
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p = Point(x, y)
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beams.add(p)
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if p not in splitters:
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next_row.add(y)
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continue
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for neighbour in (y - 1, y + 1):
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beams.add(Point(x, neighbour))
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next_row.add(neighbour)
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current_row = next_row
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return beams
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start, splitters = parse(input)
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beams = run_manifold(start, splitters)
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return len(beams & splitters)
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def main() -> None:
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input = sys.stdin.read().splitlines()
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print(solve(input))
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if __name__ == "__main__":
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main()
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