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19 lines
509 B
19 lines
509 B
# https://adventofcode.com/2020/day/13
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using AdventOfCode
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using Mods
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t_str, buses_str = readlines("2020/data/day_13.txt")
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time = parse(Int, t_str)
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buses = map(x->x=="x" ? nothing : parse(Int, x), split(buses_str, ','))
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function part_1()
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wait, bus = min(map(x->(x*ceil(time / x), x), filter(!isnothing, buses))...)
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(wait - time) * bus
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end
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@info part_1()
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function part_2()
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mods = map(k->Mod{buses[k]}(-(k-1)), filter(k->!isnothing(buses[k]), keys(buses)))
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CRT(mods...).val
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end
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@info part_2()
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