103 lines
2.5 KiB
Python
103 lines
2.5 KiB
Python
from lib import get_data, Grid2D
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from math import gcd, atan2, pi
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def angle(a1, a2):
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dy = a1[0] - a2[0]
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dx = a2[1] - a1[1]
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a = (atan2(dx, dy) + 2 * pi) % (2 * pi)
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return a
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def dist(a1, a2):
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return abs(a1[0] - a2[0]) + abs(a1[1] - a2[1])
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def part_1(data):
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g = Grid2D(data)
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asts = g.find("#")
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asts_set = set(asts)
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best_ast = None
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visible_max = 0
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for a in asts:
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visible = 0
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for other in asts:
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if a == other:
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continue
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x1, x2 = a[0], other[0]
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y1, y2 = a[1], other[1]
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if y1 == y2:
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for x in range(min(x1, x2) + 1, max(x1, x2)):
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if (x, y1) in asts_set:
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break
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else:
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visible += 1
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elif x1 == x2:
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for y in range(min(y1, y2) + 1, max(y1, y2)):
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if (x1, y) in asts_set:
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break
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else:
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visible += 1
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else:
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dx = abs(x1 - x2)
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dy = abs(y1 - y2)
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g = gcd(dx, dy)
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dx //= g
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dy //= g
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x, y = x1, y1
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if x2 < x1:
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dx = -dx
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if y2 < y1:
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dy = -dy
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blocked = False
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while True:
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x += dx
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y += dy
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if (x, y) == (x2, y2):
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break
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if (x, y) in asts_set:
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blocked = True
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break
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if not blocked:
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visible += 1
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if visible > visible_max:
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visible_max = visible
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best_ast = a
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assert best_ast is not None
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print(visible_max)
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other_asts = [a for a in asts if a != best_ast]
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removed_count = 0
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while True:
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removed = set()
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other_asts = sorted(
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other_asts, key=lambda a: (angle(best_ast, a), dist(best_ast, a))
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)
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lowest_angle = -1
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for a in other_asts:
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current_angle = angle(best_ast, a)
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if current_angle > lowest_angle:
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removed.add(a)
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lowest_angle = current_angle
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removed_count += 1
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if removed_count == 200:
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print(a[1] * 100 + a[0])
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return
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other_asts = [a for a in other_asts if a not in removed]
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def main():
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data = get_data(__file__)
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part_1(data)
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if __name__ == "__main__":
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main()
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