120 lines
2.8 KiB
Elixir
120 lines
2.8 KiB
Elixir
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defmodule Day11 do
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@example """
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L.LL.LL.LL
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LLLLLLL.LL
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L.L.L..L..
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LLLL.LL.LL
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L.LL.LL.LL
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L.LLLLL.LL
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..L.L.....
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LLLLLLLLLL
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L.LLLLLL.L
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L.LLLLL.LL
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"""
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def part1(example \\ false) do
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parse_input(example)
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|> find_final_state(&count_adjacent_occupied/3, 4)
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|> count_occupied()
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end
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def part2(example \\ false) do
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parse_input(example)
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|> find_final_state(&count_visible_occupied/3, 5)
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|> count_occupied()
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# |> step(&count_visible_occupied/3, 5)
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# |> step(&count_visible_occupied/3, 5)
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# |> Enum.each(&IO.puts/1)
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end
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def parse_input(example) do
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if(example, do: @example, else: File.read!("lib/day11/input.txt"))
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|> String.trim()
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|> String.split()
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|> Enum.map(&String.to_charlist/1)
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end
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def find_final_state(map, count_fn, empty_threshold) do
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case step(map, count_fn, empty_threshold) do
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^map -> map
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next -> find_final_state(next, count_fn, empty_threshold)
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end
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end
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def step(map, count_fn, empty_threshold) do
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map
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|> Enum.with_index()
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|> Enum.map(fn {row, row_index} ->
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row
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|> Enum.with_index()
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|> Enum.map(fn {el, col_index} ->
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if el == ?. do
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?.
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else
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count = count_fn.(map, row_index, col_index)
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case count do
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0 -> ?#
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c when c >= empty_threshold -> ?L
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_ -> el
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end
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end
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end)
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end)
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end
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def count_adjacent_occupied(map, row, col) do
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max(0, row - 1)..min(row + 1, length(map) - 1)
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# |> IO.inspect()
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|> Enum.map(fn test_row ->
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# IO.inspect(test_row)
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map_test_row = Enum.at(map, test_row)
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max(0, col - 1)..min(col + 1, length(map_test_row))
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|> Enum.reject(fn c -> test_row == row && c == col end)
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|> Enum.count(fn test_col ->
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Enum.at(map_test_row, test_col) == ?#
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end)
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end)
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|> Enum.sum()
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end
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@directions -1..1
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|> Enum.flat_map(fn dr ->
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-1..1
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|> Enum.map(fn dc -> {dr, dc} end)
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end)
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|> List.delete({0, 0})
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def count_visible_occupied(map, row, col) do
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Enum.count(@directions, fn {dr, dc} = dir ->
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get_visible_seat(map, row + dr, col + dc, dir) == ?#
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end)
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end
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def get_visible_seat(_, -1, _, _), do: nil
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def get_visible_seat(map, row, _, _) when row == length(map), do: nil
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def get_visible_seat(_, _, -1, _), do: nil
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def get_visible_seat(map, _, col, _) when col == length(hd(map)), do: nil
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def get_visible_seat(map, row, col, {dr, dc} = dir) do
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map
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|> Enum.at(row)
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|> Enum.at(col)
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|> case do
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?. ->
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get_visible_seat(map, row + dr, col + dc, dir)
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el ->
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el
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end
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end
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def count_occupied(map) do
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map
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|> Enum.flat_map(& &1)
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|> Enum.count(&(&1 == ?#))
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end
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end
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