26 lines
580 B
Python
26 lines
580 B
Python
from functools import reduce
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from math import gcd
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def lcm(a, b):
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return abs(a*b) // gcd(a, b)
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# f(n)=an+b and f(m)=xm+y
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# Intersection of 2 sequences -> ck+d
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def merge(a, b, x, y):
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while b != y:
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if b < y:
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b += a * ((y-b-1) // a + 1)
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else:
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y += x * ((b-y-1) // x + 1)
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d = b
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c = lcm(a, x)
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return c, d
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lines = [x.strip() for x in open("input.txt")]
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busses = ((int(x), -idx) for idx, x in enumerate(lines[1].split(',')) if x != 'x')
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sequence = reduce(lambda fn, fm: merge(*fn, *fm), busses, (1, 0))
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print(sequence[1])
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