63 lines
1.5 KiB
Python
63 lines
1.5 KiB
Python
import numpy
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N = 23
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def solve():
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lava = numpy.zeros((N,N,N), dtype=numpy.int32)
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for line in open("input"):
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x,y,z = map(int, line.strip().split(","))
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lava[x,y,z] = 1
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lava = numpy.pad(lava, (1,1), constant_values=0)
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# part 1
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area = count_touching(lava, lava^1)
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print(area)
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# part 2
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border = numpy.zeros((N,N,N), dtype=numpy.int32)
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border = numpy.pad(border, (1,1), constant_values=1)
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water = flood(lava, border)
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#print(water)
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area = count_touching(lava, water)
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print(area)
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def count_touching(A, B):
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"""counts the number of places a cell in A touches a cell in B
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(assumes a 1-cell padding around the edge which is not counted)"""
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n = 0
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for x in range(1,N+1):
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for y in range(1,N+1):
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for z in range(1,N+1):
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if A[x,y,z]:
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n += B[x-1,y,z]
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n += B[x+1,y,z]
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n += B[x,y-1,z]
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n += B[x,y+1,z]
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n += B[x,y,z-1]
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n += B[x,y,z+1]
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return n
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def flood(lava, border):
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def roll(a, axis, amount):
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return numpy.roll(a, amount, axis=axis)
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a = border
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while True:
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x = roll(a, 0, -1)
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x |= roll(a, 0, +1)
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x |= roll(a, 1, -1)
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x |= roll(a, 1, +1)
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x |= roll(a, 2, -1)
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x |= roll(a, 2, +1)
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x &= ~lava
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b = a | x
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if (a == b).all():
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return a
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a = b
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solve()
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