commit 8ceaee32a0cac77c11df36f2d55b3e7a6522fb0c · hauleth.dev/advent-of-code

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2025/day07.livemd

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       ## Part 2

     

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       ```elixir

     
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       |> Enum.sum_by(&elem(&1, 1))

     

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       ```

     

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       end)

     

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       ```

     

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       ## Part 2

     

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       ```elixir

     
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       |> Enum.sum_by(&elem(&1, 1))

     

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       ```

     

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       ## Image

     

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       ```elixir

     

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       height = length([start | rest])

     

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       width = byte_size(start)

     

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       {height, width}

     

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       ```

     

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       ```elixir

     

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       Image.new!(width, height)

     

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       |> Image.mutate(fn img ->

     

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         Image.Draw.point!(img, start_col, 0, color: :yellow)

     

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         splitters

     

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         |> Enum.with_index(1)

     

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         |> Enum.reduce(MapSet.new([start_col]), fn {splits, y}, beams ->

     

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           import MapSet, only: [intersection: 2, difference: 2, union: 2]

     

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           for x <- beams do

     

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             Image.Draw.point!(img, x, y, color: :green)

     

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           end

     

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           for x <- splits do

     

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             Image.Draw.point!(img, x, y, color: :red)

     

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           end

     

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           hits = intersection(beams, splits)

     

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           new_beams = for hit <- hits, dx <- [-1, 1], into: MapSet.new(), do: hit + dx

     

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           beams = beams |> difference(hits) |> union(new_beams)

     

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           beams

     

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         end)

     

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         #for {row, y} <- Enum.with_index(splitters, 1),

     

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         #    x <- row,

     

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         #  do: Image.Draw.point!(img, x, y, color: :red)

     

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         img

     

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       end)

     

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       |> then(fn {:ok, img} -> img end)

     

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       |> Image.resize!(5, interpolate: :nearest)

     

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       ```

     

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