119 lines
3.6 KiB
Python
119 lines
3.6 KiB
Python
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#!/usr/bin/env python
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import itertools
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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 Point3(NamedTuple):
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x: int
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y: int
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z: int
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@classmethod
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def from_input(cls, input: str) -> "Point3":
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x, y, z = map(int, input.split(","))
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return cls(x, y, z)
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@classmethod
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def neighbours(cls, p: "Point3") -> Iterator["Point3"]:
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for dx, dy, dz in (
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(0, 0, -1),
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(0, 0, 1),
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(0, -1, 0),
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(0, 1, 0),
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(-1, 0, 0),
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(1, 0, 0),
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):
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yield cls(p.x + dx, p.y + dy, p.z + dz)
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def solve(input: list[str]) -> int:
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def compute_unreachable(cubes: set[Point3]) -> set[Point3]:
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def explore(p: Point3, can_reach_out: dict[Point3, bool]) -> bool:
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seen: set[Point3] = set()
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queue: list[Point3] = [p]
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while queue:
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p = queue.pop()
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if p in seen:
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continue
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if p in can_reach_out:
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if can_reach_out[p]:
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return True
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continue # Don't go through walls
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seen.add(p)
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queue.extend(Point3.neighbours(p))
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return False
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minx, maxx = min(p.x for p in cubes), max(p.x for p in cubes)
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miny, maxy = min(p.y for p in cubes), max(p.y for p in cubes)
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minz, maxz = min(p.z for p in cubes), max(p.z for p in cubes)
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can_reach_out = {p: False for p in cubes}
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can_reach_out |= {
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Point3(x, y, z): True
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for x, (y, z) in zip(
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itertools.repeat(minx - 1),
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itertools.product(range(miny, maxy + 1), range(minz, maxz + 1)),
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)
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}
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can_reach_out |= {
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Point3(x, y, z): True
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for x, (y, z) in zip(
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itertools.repeat(maxx + 1),
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itertools.product(range(miny, maxy + 1), range(minz, maxz + 1)),
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)
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}
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can_reach_out |= {
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Point3(x, y, z): True
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for y, (x, z) in zip(
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itertools.repeat(miny - 1),
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itertools.product(range(minx, maxx + 1), range(minz, maxz + 1)),
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)
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}
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can_reach_out |= {
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Point3(x, y, z): True
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for y, (x, z) in zip(
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itertools.repeat(maxy + 1),
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itertools.product(range(minx, maxx + 1), range(minz, maxz + 1)),
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)
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}
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can_reach_out |= {
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Point3(x, y, z): True
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for z, (x, y) in zip(
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itertools.repeat(minz - 1),
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itertools.product(range(minx, maxx + 1), range(miny, maxy + 1)),
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)
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}
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can_reach_out |= {
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Point3(x, y, z): True
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for z, (x, y) in zip(
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itertools.repeat(maxz + 1),
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itertools.product(range(minx, maxx + 1), range(miny, maxy + 1)),
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)
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}
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for x, y, z in itertools.product(
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range(minx, maxx + 1),
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range(miny, maxy + 1),
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range(minz, maxz + 1),
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):
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p = Point3(x, y, z)
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can_reach_out[p] = explore(p, can_reach_out)
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return {p for p, can_reach in can_reach_out.items() if not can_reach}
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cubes = {Point3.from_input(line) for line in input}
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unreachable = compute_unreachable(cubes)
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return sum(1 for p in cubes for n in Point3.neighbours(p) if n not in unreachable)
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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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