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defmodule FourEnum do
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defstruct [:grid, :row, :col]
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end
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defmodule Four do
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defstruct [:map, :width, :height]
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def parse(input) do
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lines = input |> String.trim() |> String.split("\n")
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width = lines |> Enum.at(0) |> String.length()
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height = lines |> Enum.count()
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map =
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lines
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|> Enum.with_index()
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|> Enum.map(fn {line, row} ->
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{row,
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line
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|> String.to_charlist()
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|> Enum.with_index()
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|> Enum.map(fn {char, col} ->
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{col, char == ?@}
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end)
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|> Enum.into(%{})}
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end)
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|> Enum.into(%{})
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%Four{map: map, width: width, height: height}
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end
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def enum(%Four{} = grid),
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do: %FourEnum{grid: grid, row: 0, col: 0}
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def at_position(%Four{map: map, width: width, height: height}, r, c)
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when r >= 0 and c >= 0 and r < height and c < height,
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do: map[r][c]
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def at_position(_, _, _),
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do: nil
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end
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defimpl Enumerable, for: FourEnum do
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def count(_),
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do: {:error, __MODULE__}
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def member?(_, _),
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do: {:error, __MODULE__}
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def reduce(_enum, {:halt, acc}, _fun), do: {:halted, acc}
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def reduce(enum, {:suspend, acc}, fun), do: {:suspended, acc, &reduce(enum, &1, fun)}
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def reduce(%FourEnum{grid: %Four{map: map, width: width, height: height} = grid, row: row, col: col}, {:cont, acc}, fun) do
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cond do
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row == height ->
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{:done, acc}
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col == width - 1 ->
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reduce(%FourEnum{grid: grid, row: row + 1, col: 0}, fun.({row, col, map[row][col]}, acc), fun)
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true ->
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reduce(%FourEnum{grid: grid, row: row, col: col + 1}, fun.({row, col, map[row][col]}, acc), fun)
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end
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end
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def slice(_),
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do: {:error, __MODULE__}
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end
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input = """
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..@@.@@@@.
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@@@.@.@.@@
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@@@@@.@.@@
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@.@@@@..@.
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@@.@@@@.@@
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.@@@@@@@.@
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.@.@.@.@@@
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@.@@@.@@@@
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.@@@@@@@@.
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@.@.@@@.@.
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"""
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input = File.read!("4.input")
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grid = Four.parse(input)
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Enum.sum_by(Four.enum(grid), fn {row, col, set} ->
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if set and Enum.sum_by(row - 1..row + 1, fn r -> Enum.sum_by(col - 1..col + 1, fn c -> if(!(r == row and c == col) and Four.at_position(grid, r, c) == true, do: 1, else: 0) end) end) < 4 do
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1
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else
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0
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end
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end) |> IO.inspect()
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