diff --git a/2019/d10/ex2/ex2.py b/2019/d10/ex2/ex2.py new file mode 100755 index 0000000..480234e --- /dev/null +++ b/2019/d10/ex2/ex2.py @@ -0,0 +1,86 @@ +#!/usr/bin/env python + +import sys +from cmath import phase +from itertools import groupby +from math import gcd, pi +from typing import NamedTuple, Set, Tuple + + +class Position(NamedTuple): + x: int + y: int + + +def pos_to_angle_dist(pos: Position) -> Tuple[float, float]: + cartesian = complex(*pos) + angle = phase(cartesian) + if angle < -pi / 2: + angle += 2.5 * pi + else: + angle += pi / 2 + return (angle, abs(cartesian)) + + +def main() -> None: + asteroids = [ + Position(x, y) + for y, line in enumerate(sys.stdin.readlines()) + for x, c in enumerate(line.rstrip()) + if c == "#" + ] + + def count_spotted(x: int, y: int) -> int: + seen: Set[Position] = set() + ans = 0 + radius = 1 + + while True: + + def is_r_away(pos: Position) -> bool: + return max(abs(pos.x - x), abs(pos.y - y)) == radius + + to_visit = list(filter(is_r_away, asteroids)) + radius += 1 + if len(to_visit) == 0: + break + for pos in to_visit: + rel = (pos.x - x, pos.y - y) + common = gcd(*rel) + rel = Position(*(a // common for a in rel)) + if rel in seen: + continue # Already have an asteroid on this path + seen.add(rel) + ans += 1 + + return ans + + # We need to find the observatory's position as a prerequisite + ans, orig = max((count_spotted(*pos), pos) for pos in asteroids) + print(f"({orig.x}, {orig.y}): {ans}") + + def to_rel(p: Position) -> Position: + return Position(*(a - o for (a, o) in zip(p, orig))) + + angle_dists = sorted( + (pos_to_angle_dist(to_rel(p)), p) for p in asteroids if p != orig + ) + grouped_angle_dists = [ + [val[1] for val in group] + for __, group in groupby(angle_dists, key=lambda x: x[0][0]) + ] + + def find_n_th(n: int) -> Position: + assert 0 < n < len(asteroids) # Sanity check + while n >= len(grouped_angle_dists): + for group in grouped_angle_dists: + group.pop(0) + n -= 1 + return grouped_angle_dists[n - 1][0] + + x, y = find_n_th(200) + print(x * 100 + y) + + +if __name__ == "__main__": + main()