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94 lines
2.2 KiB
94 lines
2.2 KiB
12 months ago
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require "matrix"
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# part one
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plan = ARGF.read.scan(/([UDLR])\s+(\d+)\s+\(#(\w+)\)/)
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.map { [_1.to_sym, _2.to_i, _3] }
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# part two
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plan = plan.map { _3.chars }.map {|hex|
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dist = hex[0..4].join.to_i(16)
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dir = "RDLU".chars.fetch(hex.last.to_i).to_sym
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[dir, dist]
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}
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deltas = { U: [-1,0], D: [1,0], L: [0,-1], R: [0,1] }
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points = plan.inject([[0,0]]) {|points, (dir, dist, _)|
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delta = deltas.fetch(dir).map { _1*dist }
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next_point = points.last.zip(delta).map { _1 + _2 }
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points << next_point
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}
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p [
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(0.5 * points.each_cons(2).sum { Matrix.columns(_1).determinant }.abs).to_i,
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plan.select {|dir,_,_| %i[ D L ].include?(dir) }.sum { _2 },
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1,
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].sum
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# trench = plan.inject([[0,0]]) {|trench, (dir, dist, _)|
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# delta = deltas.fetch(dir)
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# dist.times do
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# trench << trench.last.zip(delta).map { _1 + _2 }
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# end
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# trench
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# }.uniq
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# y_range = Range.new(*trench.map(&:first).minmax)
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# x_range = Range.new(*trench.map(&:last).minmax)
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# y_range.each do |y|
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# x_range.each do |x|
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# print trench.include?([y,x]) ? ?# : ?.
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# end
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# puts
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# end
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# part one
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# lagoon = trench.to_set
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# seed = [1, x_range.find {|x| lagoon.include?([0,x]) } + 1]
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# frontier = [seed]
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# until frontier.empty?
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# current = frontier.shift
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# lagoon << current
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# frontier.concat(
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# [[-1,0],[1,0],[0,-1],[0,1]].map {|delta|
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# current.zip(delta).map { _1 + _2 }
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# }.reject { lagoon.include?(_1) || frontier.include?(_1) }
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# )
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# end
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# p lagoon.size
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# row_counts = {}
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# count = trench.size
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# y_range.each do |y|
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# inside = nil
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# segments = trench.select {|y_,_| y_ == y }.map(&:last).sort.slice_when { _1+1 != _2 }
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# if row_count = row_counts[segments]
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# count += row_count
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# next
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# end
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# row_count = 0
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# segments.each do |segment|
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# if [-1,1].all? {|dy| [[y+dy,segment[0]],[y+dy,segment[-1]]].any? { trench.include?(_1) }}
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# if inside
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# row_count += segment[0] - inside
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# inside = nil
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# else
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# inside = segment[-1] + 1
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# end
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# elsif inside
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# row_count += segment[0] - inside
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# inside = segment[-1] + 1
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# end
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# end
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# row_counts[segments] = row_count
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# count += row_count
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# end
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# p count
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