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input = ARGF.readlines(chomp: true)
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.flat_map.with_index {|row, y|
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row.chars.map.with_index {|elem, x| [[y,x], elem] }
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}.to_h
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count_energized = ->(start, dir) {
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|
current = [[start, dir]]
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seen = Set.new
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until current.empty?
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coord, delta = current.shift
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seen << [coord, delta]
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next_delta = case [input[coord], delta]
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in [nil, _]
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[] # the beam has escaped the contraption
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in [?., _] | [?|, [_,0]] | [?-, [0,_]] # keep going
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[delta]
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in [?|, [0,_]] # split up and down
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[[-1,0], [1,0]]
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in [?-, [_,0]] # split left and right
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[[0,-1], [0,1]]
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in [?/, _]
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|
[delta.map { -_1 }.reverse]
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in [?\\, _]
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[delta.reverse]
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else
|
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fail
|
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end
|
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|
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current.concat(
|
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|
next_delta
|
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|
|
.map {|d| [coord.zip(d).map { _1 + _2 }, d] }
|
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|
|
.reject { seen.include?(_1) }
|
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|
|
)
|
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|
|
end
|
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|
|
seen.map(&:first).select { input.has_key?(_1) }.uniq.size
|
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|
|
|
}
|
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|
|
|
|
|
|
|
max_y = input.keys.map(&:first).max
|
|
|
|
|
max_x = input.keys.map(&:last).max
|
|
|
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|
|
|
|
|
|
candidates = [
|
|
|
|
|
(0..max_x).map { [[0,_1], [1,0]] }, # down
|
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|
|
|
(0..max_x).map { [[max_y,_1], [-1,0]] }, # up
|
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|
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|
(0..max_y).map { [[_1,0], [0,1]] }, # right
|
|
|
|
|
(0..max_y).map { [[_1,max_x], [0,-1]] }, # left
|
|
|
|
|
].inject(:+)
|
|
|
|
|
|
|
|
|
|
p candidates.map { count_energized[*_1] }.max
|
