145 lines
3.5 KiB
Python
145 lines
3.5 KiB
Python
# -*- encoding: utf-8 -*-
|
|
|
|
import sys
|
|
from collections import defaultdict
|
|
from enum import Enum, auto
|
|
from typing import Callable, cast
|
|
|
|
|
|
class Cell(Enum):
|
|
AIR = auto()
|
|
ROCK = auto()
|
|
SAND = auto()
|
|
|
|
def __str__(self) -> str:
|
|
return {Cell.AIR: ".", Cell.ROCK: "#", Cell.SAND: "O"}[self]
|
|
|
|
|
|
def print_blocks(blocks: dict[tuple[int, int], Cell]):
|
|
"""
|
|
Print the given set of blocks on a grid.
|
|
|
|
Args:
|
|
blocks: Set of blocks to print.
|
|
"""
|
|
x_min, y_min, x_max, y_max = (
|
|
min(x for x, y in blocks),
|
|
0,
|
|
max(x for x, y in blocks),
|
|
max(y for x, y in blocks),
|
|
)
|
|
|
|
for y in range(y_min, y_max + 1):
|
|
print(
|
|
"".join(str(blocks.get((x, y), Cell.AIR)) for x in range(x_min, x_max + 1))
|
|
)
|
|
|
|
|
|
def flow(
|
|
blocks: dict[tuple[int, int], Cell],
|
|
stop_fn: Callable[[int, int], bool],
|
|
fill_fn: Callable[[int, int], Cell],
|
|
) -> dict[tuple[int, int], Cell]:
|
|
"""
|
|
Flow sands onto the given set of blocks
|
|
|
|
Args:
|
|
blocks: Blocks containing ROCK position. Modified in-place.
|
|
stop_fn: Function called with the last (assumed) position of a grain of
|
|
sand BEFORE adding it to blocks. If the function returns True, the grain
|
|
is added and a new one is flowed, otherwise, the whole procedure stops
|
|
and the function returns (without adding the final grain).
|
|
fill_fn: Function called when the target position of a grain (during the
|
|
flowing process) is missing from blocks.
|
|
|
|
Returns:
|
|
The input blocks.
|
|
"""
|
|
|
|
y_max = max(y for x, y in blocks)
|
|
|
|
while True:
|
|
x, y = 500, 0
|
|
|
|
while y <= y_max:
|
|
|
|
moved = False
|
|
for cx, cy in ((x, y + 1), (x - 1, y + 1), (x + 1, y + 1)):
|
|
if (cx, cy) not in blocks and fill_fn(cx, cy) == Cell.AIR:
|
|
x, y = cx, cy
|
|
moved = True
|
|
elif blocks[cx, cy] == Cell.AIR:
|
|
x, y = cx, cy
|
|
moved = True
|
|
|
|
if moved:
|
|
break
|
|
|
|
if not moved:
|
|
break
|
|
|
|
if stop_fn(x, y):
|
|
break
|
|
|
|
blocks[x, y] = Cell.SAND
|
|
|
|
return blocks
|
|
|
|
|
|
# === inputs ===
|
|
|
|
lines = sys.stdin.read().splitlines()
|
|
|
|
paths: list[list[tuple[int, int]]] = []
|
|
for line in lines:
|
|
parts = line.split(" -> ")
|
|
paths.append(
|
|
[
|
|
cast(tuple[int, int], tuple(int(c.strip()) for c in part.split(",")))
|
|
for part in parts
|
|
]
|
|
)
|
|
|
|
|
|
blocks: dict[tuple[int, int], Cell] = {}
|
|
for path in paths:
|
|
for start, end in zip(path[:-1], path[1:]):
|
|
x_start = min(start[0], end[0])
|
|
x_end = max(start[0], end[0]) + 1
|
|
y_start = min(start[1], end[1])
|
|
y_end = max(start[1], end[1]) + 1
|
|
|
|
for x in range(x_start, x_end):
|
|
for y in range(y_start, y_end):
|
|
blocks[x, y] = Cell.ROCK
|
|
|
|
print_blocks(blocks)
|
|
print()
|
|
|
|
x_min, y_min, x_max, y_max = (
|
|
min(x for x, y in blocks),
|
|
0,
|
|
max(x for x, y in blocks),
|
|
max(y for x, y in blocks),
|
|
)
|
|
|
|
# === part 1 ===
|
|
|
|
blocks_1 = flow(
|
|
blocks.copy(), stop_fn=lambda x, y: y > y_max, fill_fn=lambda x, y: Cell.AIR
|
|
)
|
|
print_blocks(blocks_1)
|
|
print(f"answer 1 is {sum(v == Cell.SAND for v in blocks_1.values())}")
|
|
print()
|
|
|
|
# === part 2 ===
|
|
|
|
blocks_2 = flow(
|
|
blocks.copy(),
|
|
stop_fn=lambda x, y: x == 500 and y == 0,
|
|
fill_fn=lambda x, y: Cell.AIR if y < y_max + 2 else Cell.ROCK,
|
|
)
|
|
blocks_2[500, 0] = Cell.SAND
|
|
print_blocks(blocks_2)
|
|
print(f"answer 2 is {sum(v == Cell.SAND for v in blocks_2.values())}")
|