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48 lines
1.7 KiB
48 lines
1.7 KiB
9 months ago
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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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current = [[[0,0], [0,1]]]
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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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case [elem = 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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current << [coord.zip(delta).map { _1 + _2 }, delta]
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in [?|, [0,_]] # split up and down
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current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
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current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
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in [?-, [_,0]] # split left and right
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current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
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current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
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in [?/, [0,1]] # going right, goes up
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current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
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in [?/, [0,-1]] # going left, goes down
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current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
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in [?/, [1,0]] # going down, goes left
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current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
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in [?/, [-1,0]] # going up, goes right
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current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
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in [?\\, [0,1]] # going right, goes down
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current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
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in [?\\, [0,-1]] # going left, goes up
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current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
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in [?\\, [1,0]] # going down, goes right
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current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
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in [?\\, [-1,0]] # going up, goes left
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current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
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else
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fail "unexpected element: #{elem.inspect}"
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end
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current = current.reject { seen.include?(_1) }
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end
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p seen.map(&:first).select { input.has_key?(_1) }.uniq.size
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