92 lines
2.2 KiB
Elixir
92 lines
2.2 KiB
Elixir
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defmodule AOC.Day11 do
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@x_size 95
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@y_size 93
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def parse_input do
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AOC.Util.input_lines(11, 1)
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|> Enum.with_index()
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|> Enum.reduce(%{}, fn {line, y}, acc ->
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line
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|> String.split("", trim: true)
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|> Enum.with_index()
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|> Enum.reject(&(elem(&1, 0) == "."))
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|> Enum.map(fn {_, i} -> {false, i} end)
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|> Enum.into(acc, fn {c, x} -> {{x, y}, c} end)
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end)
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end
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def count_direct_adj(seats, {x, y}) do
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[
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{x - 1, y - 1},
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{x - 1, y},
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{x - 1, y + 1},
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{x, y - 1},
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{x, y + 1},
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{x + 1, y - 1},
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{x + 1, y},
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{x + 1, y + 1}
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]
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|> Enum.count(fn coords -> Map.get(seats, coords) end)
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end
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def look_direction(seats, coords, next_fun) do
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{x, y} = coords = next_fun.(coords)
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if x not in 0..@x_size or y not in 0..@y_size do
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false
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else
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case Map.get(seats, coords) do
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nil -> look_direction(seats, coords, next_fun)
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x -> x
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end
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end
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end
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def count_sight_adj(seats, {x, y}) do
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[
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fn {x, y} -> {x + 1, y + 1} end,
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fn {x, y} -> {x + 1, y - 1} end,
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fn {x, y} -> {x - 1, y + 1} end,
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fn {x, y} -> {x - 1, y - 1} end,
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fn {x, y} -> {x + 1, y} end,
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fn {x, y} -> {x - 1, y} end,
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fn {x, y} -> {x, y + 1} end,
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fn {x, y} -> {x, y - 1} end
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]
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|> Enum.count(&look_direction(seats, {x, y}, &1))
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end
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def simulate_round(seats, count_adj, min) do
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Enum.reduce(seats, {%{}, false}, fn {coords, x}, {acc, changed} ->
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new =
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case {x, count_adj.(seats, coords)} do
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{false, 0} -> true
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{true, count} when count >= min -> false
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_ -> x
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end
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{Map.put(acc, coords, new), changed or new != x}
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end)
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end
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def find_stable(seats, count_adj, min) do
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{seats, changed} = simulate_round(seats, count_adj, min)
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if changed do
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find_stable(seats, count_adj, min)
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else
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seats
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end
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end
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def parts do
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input = parse_input()
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stable = find_stable(input, &count_direct_adj/2, 4)
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part1 = Enum.count(stable, &elem(&1, 1))
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stable = find_stable(input, &count_sight_adj/2, 5)
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part2 = Enum.count(stable, &elem(&1, 1))
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{part1, part2}
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end
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end
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