47 lines
1.7 KiB
Python
Executable File
47 lines
1.7 KiB
Python
Executable File
#!/usr/bin/env python3
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from useful import *
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from fractions import Fraction
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debug = False
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if len(sys.argv) >= 2 and sys.argv[1] == '-v':
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debug = True
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sys.argv = sys.argv[:1] + sys.argv[2:]
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def makelin(l):
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px, py, _, vx, vy, _ = numbers(l)
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a = Fraction(vy, vx)
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b = py - px * a
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return a, b, px, vx > 0
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lins = [makelin(l) for l in lines(open(0))]
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bot = 200000000000000 if len(sys.argv) < 2 else int(sys.argv[1])
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top = 400000000000000 if len(sys.argv) < 3 else int(sys.argv[2])
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total = 0
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for (a1, b1, px1, vx1_is_pos), (a2, b2, px2, vx2_is_pos) in combinations(lins, 2):
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if debug:
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print('Hailstone A: Moving from %s in a %s direction' % (
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px1, 'positive' if vx1_is_pos else 'negative'), file=sys.stderr)
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print('Hailstone B: %sx + %s = %sx + %s ?' % (a1, b1, a2, b2), file=sys.stderr)
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if a1 == a2:
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if debug:
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print('Hailstones\' paths are parallel; they never intersect.\n', file=sys.stderr)
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else:
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ad, bd = (a1 - a2), (b2 - b1)
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x = bd / ad
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y = a1 * x + b1
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y_sanity = a2 * x + b2
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assert y == y_sanity
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if bot <= x <= top and bot <= y <= top:
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if (x < px1) != vx1_is_pos and (x < px2) != vx2_is_pos: # "xor"
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if debug:
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print('Hailstones\' paths will intersect (at x=%s, y=%s).\n' % (x, y), file=sys.stderr)
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total += 1
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else:
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if debug:
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print('Hailstones\' paths intersected in the past (at x=%s, y=%s).\n' % (x, y), file=sys.stderr)
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else:
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if debug:
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print('Hailstones\' paths cross sometime (at x=%s, y=%s).\n' % (x, y), file=sys.stderr)
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print(total)
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