158 lines
4.2 KiB
Python
Executable file
158 lines
4.2 KiB
Python
Executable file
#!/usr/bin/env python
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import enum
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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 Point(NamedTuple):
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x: int
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y: int
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def __add__(self, other):
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if not isinstance(other, Point):
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return NotImplemented
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return Point(self.x + other.x, self.y + other.y)
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def __sub__(self, other):
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if not isinstance(other, Point):
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return NotImplemented
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return Point(self.x - other.x, self.y - other.y)
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def translate(points: set[Point], delta: Point) -> set[Point]:
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return {p + delta for p in points}
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class Rock(str, enum.Enum):
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LINE = "####"
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PLUS = ".#.\n###\n.#."
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CORNER = "..#\n..#\n###"
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VERTICAL_LINE = "#\n#\n#\n#"
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SQUARE = "##\n##"
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@classmethod
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def stream(cls) -> Iterator["Rock"]:
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yield from itertools.cycle(iter(cls))
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def to_points(self) -> set[Point]:
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res: set[Point] = set()
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for y, line in enumerate(reversed(self.splitlines())):
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for x, c in enumerate(line):
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if c == ".":
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continue
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res.add(Point(x, y))
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return res
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class JetStream(str, enum.Enum):
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LEFT = "<"
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RIGHT = ">"
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@classmethod
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def stream(cls, jet_pattern: str) -> Iterator["JetStream"]:
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yield from itertools.cycle(map(cls, jet_pattern))
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def as_delta(self) -> Point:
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if self == self.LEFT:
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return Point(-1, 0)
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if self == self.RIGHT:
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return Point(1, 0)
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assert False # Sanity check
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def solve(input: list[str]) -> int:
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fallen_stack: set[Point] = set()
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max_height = 0
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LEFT_WALL = -1
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RIGHT_WALL = 7
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FLOOR = 0
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rocks = list(iter(Rock))
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jet_stream = [JetStream(c) for c in input[0]]
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t = 0
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jet_index = 0
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rock_index = 0
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def step(rock: set[Point], jet: JetStream) -> tuple[set[Point], bool]:
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# Check if it can be pushed by the jet, or if it hits an obstacle
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pushed_rock = translate(rock, jet.as_delta())
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if not (fallen_stack & pushed_rock) and all(
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LEFT_WALL < p.x < RIGHT_WALL for p in pushed_rock
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):
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rock = pushed_rock
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# Check if it can go down
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fallen_rock = translate(rock, Point(0, -1))
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if not (fallen_stack & fallen_rock) and all(p.y > FLOOR for p in fallen_rock):
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return fallen_rock, True
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return rock, False
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def simulate_rock_fall() -> None:
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nonlocal max_height
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nonlocal jet_index
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nonlocal rock_index
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rock = rocks[rock_index].to_points()
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# Align 2 units away from LEFT_WALL and 3 higher than
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# current stack
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rock = translate(rock, Point(2, max_height + 3 + 1))
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while True:
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rock, keep_going = step(rock, jet_stream[jet_index])
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jet_index = (jet_index + 1) % len(jet_stream)
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if not keep_going:
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break
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fallen_stack.update(rock)
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max_height = max(max_height, max(p.y for p in rock))
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rock_index = (rock_index + 1) % len(rocks)
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StackStateHash = tuple[int, int, frozenset[Point]]
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def stack_state_hash() -> StackStateHash:
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top = frozenset(
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Point(p.x, p.y - max_height)
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for p in fallen_stack
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if p.y >= (max_height - 50) # Cut-off point chosen arbitrarily...
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)
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return rock_index, jet_index, top
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assert len(input) == 1 # Sanity check
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cache: dict[StackStateHash, tuple[int, int]] = {}
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added_height = 0
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END_OF_SIMULATION = 1_000_000_000_000
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while t < END_OF_SIMULATION:
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simulate_rock_fall()
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t += 1
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stack_hash = stack_state_hash()
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if stack_hash in cache:
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previous_t, previous_height = cache[stack_hash]
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cycle_length = t - previous_t
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num_cycles = (END_OF_SIMULATION - t) // cycle_length
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added_height += num_cycles * (max_height - previous_height)
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t += num_cycles * cycle_length
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else:
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cache[stack_hash] = t, max_height
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return max_height + added_height
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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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