88 lines
2.3 KiB
Python
88 lines
2.3 KiB
Python
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#!/usr/bin/env python
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import sys
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from cmath import phase
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from itertools import groupby
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from math import gcd, pi
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from pprint import pprint
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from typing import NamedTuple, Set, Tuple
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class Position(NamedTuple):
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x: int
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y: int
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def pos_to_angle_dist(pos: Position) -> Tuple[float, float]:
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cartesian = complex(*pos)
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angle = phase(cartesian)
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if angle < -pi / 2:
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angle += 2.5 * pi
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else:
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angle += pi / 2
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return (angle, abs(cartesian))
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def main() -> None:
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asteroids = [
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Position(x, y)
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for y, line in enumerate(sys.stdin.readlines())
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for x, c in enumerate(line.rstrip())
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if c == "#"
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]
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def count_spotted(x: int, y: int) -> int:
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seen: Set[Position] = set()
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ans = 0
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radius = 1
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while True:
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def is_r_away(pos: Position) -> bool:
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return max(abs(pos.x - x), abs(pos.y - y)) == radius
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to_visit = list(filter(is_r_away, asteroids))
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radius += 1
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if len(to_visit) == 0:
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break
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for pos in to_visit:
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rel = (pos.x - x, pos.y - y)
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common = gcd(*rel)
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rel = Position(*(a // common for a in rel))
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if rel in seen:
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continue # Already have an asteroid on this path
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seen.add(rel)
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ans += 1
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return ans
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# We need to find the observatory's position as a prerequisite
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ans, orig = max((count_spotted(*pos), pos) for pos in asteroids)
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print(f"({orig.x}, {orig.y}): {ans}")
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def to_rel(p: Position) -> Position:
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return Position(*(a - o for (a, o) in zip(p, orig)))
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angle_dists = sorted(
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(pos_to_angle_dist(to_rel(p)), p) for p in asteroids if p != orig
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)
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grouped_angle_dists = [
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[val[1] for val in group]
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for __, group in groupby(angle_dists, key=lambda x: x[0][0])
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]
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def find_n_th(n: int) -> Position:
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assert 0 < n < len(asteroids) # Sanity check
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while n >= len(grouped_angle_dists):
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for group in grouped_angle_dists:
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group.pop(0)
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n -= 1
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return grouped_angle_dists[n - 1][0]
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x, y = find_n_th(200)
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print(x * 100 + y)
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if __name__ == "__main__":
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main()
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