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52 lines
1.2 KiB
52 lines
1.2 KiB
heights = ARGF.read.lines(chomp: true).map(&:chars)
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.each.with_index.with_object({}) do |(row,y),map|
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row.each.with_index do |height,x|
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map[[y,x]] = height
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end
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end
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class HeightMap
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def initialize(heights)
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@heights = heights
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end
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def shortest(from:, to:, &cond)
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queue = [from]
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visited = { from => 0 }
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until queue.empty? || to.any? { visited.has_key?(_1) }
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current = queue.shift
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moves = visited.fetch(current)
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neighbors = [
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[-1, 0],
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[ 1, 0],
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[ 0, -1],
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[ 0, 1],
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].map { current.zip(_1).map {|a,b| a + b } }
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.select { @heights.has_key?(_1) }
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.reject { visited.has_key?(_1) }
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.select { cond.([@heights.fetch(current), @heights.fetch(_1)]) }
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neighbors.each do |y,x|
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visited[[y,x]] = moves + 1
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queue << [y,x]
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end
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queue.sort_by { visited.fetch(_1) }
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end
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visited.find {|k,v| to.include?(k) }.last
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end
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end
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s, e = heights.invert.values_at(?S, ?E)
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heights[s] = ?a
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heights[e] = ?z
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hm = HeightMap.new(heights)
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p hm.shortest(from: s, to: [e]) { _1.ord + 1 >= _2.ord }
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as = heights.select { _2 == ?a }.map(&:first)
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p hm.shortest(from: e, to: as) { _1.ord - 1 <= _2.ord }
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