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73 lines
2 KiB
Python
73 lines
2 KiB
Python
from dataclasses import dataclass
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@dataclass
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class Asteroid:
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x: int
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y: int
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def __hash__(self):
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return hash((self.x, self.y))
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@staticmethod
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def square_length(a: "Asteroid", b: "Asteroid"):
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return (b.x - a.x) * (b.x - a.x) + (b.y - a.y) * (b.y - a.y)
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@staticmethod
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def cross_product(a: "Asteroid", b: "Asteroid", c: "Asteroid"):
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return (c.y - a.y) * (b.x - a.x) - (c.x - a.x) * (b.y - a.y)
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@staticmethod
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def dot_product(a: "Asteroid", b: "Asteroid", c: "Asteroid"):
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return (c.x - a.x) * (b.x - a.x) + (c.y - a.y) * (b.y - a.y)
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@staticmethod
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def is_between(a: "Asteroid", b: "Asteroid", c: "Asteroid"):
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"""Check if c is between a and b."""
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cross_product = Asteroid.cross_product(a, b, c)
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# compare versus epsilon for floating point values, or != 0 if using integers
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if abs(cross_product) != 0:
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return False
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dot_product = Asteroid.dot_product(a, b, c)
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if dot_product < 0:
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return False
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squared_length_ba = Asteroid.square_length(a, b)
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if dot_product > squared_length_ba:
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return False
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return True
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def can_see(self, other: "Asteroid", asteroids: set["Asteroid"]) -> bool:
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for asteroid in asteroids:
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if asteroid in [self, other]:
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continue
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if Asteroid.is_between(self, other, asteroid):
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return False
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return True
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def main():
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asteroids = set()
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with open("inputs/day10") as f:
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for y, line in enumerate(f):
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for x, pixel in enumerate(line):
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if pixel == "#":
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asteroids.add(Asteroid(x, y))
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max_visible = 0
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for source in asteroids:
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visible = 0
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for destination in asteroids:
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if destination != source and source.can_see(destination, asteroids):
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visible += 1
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if visible > max_visible:
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max_visible = visible
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print(max_visible)
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if __name__ == "__main__":
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main()
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