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30 lines
720 B
30 lines
720 B
adapters = ARGF.read.scan(/\d+/).map(&:to_i)
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outlet = 0
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device = adapters.max + 3
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dist = (adapters + [outlet, device]).sort.each_cons(2).map {|a,b| b - a }
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# part 1
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# tally = dist.tally
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# p dist[1] * dist[3]
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# programmatically figuring out the arrangements
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# arrangements = Hash.new {|h,k|
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# h[k] = (0..k-1).flat_map {|n| (2..k).to_a.combination(n).to_a }
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# .reject {|c| (c << 1 << k+1).sort.each_cons(2).any? {|a,b| b-a > 3 }}
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# .count
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# }
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# tribonacci
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arrangements = Hash.new {|h,k| h[k] = h[k-1] + h[k-2] + h[k-3] }
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arrangements[0] = 1
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arrangements[1] = 1
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arrangements[2] = 2
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p dist
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.slice_when {|a,b| a != b }
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.select {|run| run.first == 1 }
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.map {|run| arrangements[run.size] }
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.inject(&:*)
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