mirror of
https://github.com/bertptrs/adventofcode.git
synced 2025-12-25 21:00:31 +01:00
94 lines
2.0 KiB
Python
94 lines
2.0 KiB
Python
import math
|
|
from collections import defaultdict
|
|
from typing import TextIO, Tuple
|
|
|
|
import numpy # type: ignore
|
|
|
|
|
|
def read_asteroids(data: TextIO) -> Tuple[numpy.array, numpy.array]:
|
|
xs = []
|
|
ys = []
|
|
for y, line in enumerate(data):
|
|
for x, c in enumerate(line):
|
|
if c == '#':
|
|
xs.append(x)
|
|
ys.append(y)
|
|
|
|
return numpy.array(xs), -numpy.array(ys)
|
|
|
|
|
|
def asteroids_visible(x: int, y: int, xs: numpy.array, ys: numpy.array) -> int:
|
|
dx = xs - x
|
|
dy = ys - y
|
|
|
|
div = numpy.abs(numpy.gcd(dx, dy))
|
|
|
|
mask = div != 0
|
|
|
|
dx[mask] //= div[mask]
|
|
dy[mask] //= div[mask]
|
|
|
|
unique = set(zip(dx, dy))
|
|
|
|
return len(unique) - 1 # need to ignore the point itself
|
|
|
|
|
|
def part1(data: TextIO) -> int:
|
|
xs, ys = read_asteroids(data)
|
|
|
|
return max(asteroids_visible(x, y, xs, ys) for x, y in zip(xs, ys))
|
|
|
|
|
|
def part2(data: TextIO) -> int:
|
|
xs, ys = read_asteroids(data)
|
|
|
|
cx, cy = max(zip(xs, ys), key=lambda c: asteroids_visible(c[0], c[1], xs, ys))
|
|
|
|
dx = xs - cx
|
|
dy = ys - cy
|
|
|
|
angles = numpy.arctan2(dy, dx)
|
|
distances = numpy.abs(dx) + numpy.abs(dy)
|
|
|
|
to_shoot = defaultdict(list)
|
|
|
|
for angle, distance, dx, dy in zip(angles, distances, dx, dy):
|
|
if distance == 0:
|
|
# The point itself
|
|
continue
|
|
|
|
to_shoot[angle].append((distance, dx, dy))
|
|
|
|
for distances in to_shoot.values():
|
|
distances.sort(reverse=True)
|
|
|
|
unique_angles = sorted(set(angles), reverse=True)
|
|
|
|
shot = 0
|
|
|
|
# First shoot from up clockwise
|
|
for angle in unique_angles:
|
|
if angle > math.pi / 2:
|
|
continue
|
|
|
|
shot += 1
|
|
|
|
_, dx, dy = to_shoot[angle].pop()
|
|
|
|
# Repeatedly shoot until you reach #200
|
|
while True:
|
|
for angle in unique_angles:
|
|
if not to_shoot[angle]:
|
|
# Nothing left to shoot
|
|
continue
|
|
|
|
shot += 1
|
|
|
|
_, dx, dy = to_shoot[angle].pop()
|
|
|
|
if shot == 200:
|
|
x = cx + dx
|
|
y = -(cy + dy)
|
|
return 100 * x + y
|
|
|