115 lines
3 KiB
Elixir
115 lines
3 KiB
Elixir
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defmodule AOC.Day14 do
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use AOC.Day, day: 14
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@compile {:parse_transform, :ms_transform}
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def parse_input(lines) do
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dish_table = :ets.new(:dish_table, [])
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lines
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|> Enum.with_index()
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|> Enum.each(fn {line, y} ->
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line
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|> String.to_charlist()
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|> Enum.with_index()
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|> Enum.each(fn
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{?O, x} -> :ets.insert(dish_table, {{y, x}, :round})
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{?#, x} -> :ets.insert(dish_table, {{y, x}, :cube})
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{?., _x} -> :ok
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end)
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end)
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max_y =
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:ets.tab2list(dish_table)
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|> Enum.map(&elem(&1, 0))
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|> Enum.map(&elem(&1, 0))
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|> Enum.max()
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max_x =
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:ets.tab2list(dish_table)
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|> Enum.map(&elem(&1, 0))
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|> Enum.map(&elem(&1, 1))
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|> Enum.max()
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{dish_table, {max_y, max_x}}
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end
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def get_round_rock_coords(dish_table) do
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:ets.select(dish_table, :ets.fun2ms(fn {coords, type} when type == :round -> coords end))
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end
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def perform_spin_cycle(dish_table, max_coords) do
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slide(dish_table, max_coords, fn {y1, _}, {y2, _} -> y1 <= y2 end, fn {y, x} ->
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{y - 1, x}
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end)
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slide(dish_table, max_coords, fn {_, x1}, {_, x2} -> x1 <= x2 end, fn {y, x} ->
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{y, x - 1}
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end)
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slide(dish_table, max_coords, fn {y1, _}, {y2, _} -> y1 >= y2 end, fn {y, x} ->
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{y + 1, x}
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end)
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slide(dish_table, max_coords, fn {_, x1}, {_, x2} -> x1 >= x2 end, fn {y, x} ->
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{y, x + 1}
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end)
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end
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def slide(dish_table, max_coords, sort_fun, slide_fun) do
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get_round_rock_coords(dish_table)
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|> Enum.sort(sort_fun)
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|> Enum.each(&slide_rock(dish_table, max_coords, slide_fun, &1))
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end
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def slide_rock(dish_table, {max_y, max_x} = max_coords, slide_fun, coords) do
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{slide_y, slide_x} = slide_coords = slide_fun.(coords)
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if not (slide_y < 0 or slide_x < 0 or slide_y > max_y or slide_x > max_x) do
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case :ets.lookup(dish_table, slide_coords) do
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[] ->
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:ets.delete(dish_table, coords)
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:ets.insert(dish_table, {slide_coords, :round})
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slide_rock(dish_table, max_coords, slide_fun, slide_coords)
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_ ->
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:ok
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end
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end
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end
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def calculate_total_load(dish_table, {max_y, _}) do
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get_round_rock_coords(dish_table)
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|> Enum.map(&elem(&1, 0))
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|> Enum.map(&(max_y + 1 - &1))
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|> Enum.sum()
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end
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def part1({dish_table, max_coords}) do
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slide(dish_table, max_coords, fn {y1, _}, {y2, _} -> y1 <= y2 end, fn {y, x} ->
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{y - 1, x}
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end)
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calculate_total_load(dish_table, max_coords)
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end
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def part2({dish_table, max_coords}) do
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memo_table = :ets.new(:memo_table, [])
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# Adjust according to calculations
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cycle_count = 109
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Enum.each(1..cycle_count, fn i ->
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perform_spin_cycle(dish_table, max_coords)
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memo = get_round_rock_coords(dish_table) |> Enum.sort()
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case :ets.lookup(memo_table, memo) do
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[] -> :ets.insert(memo_table, {memo, i})
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[{_, i_prev}] -> IO.puts("State already observed: #{i_prev} & #{i}")
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end
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end)
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calculate_total_load(dish_table, max_coords)
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end
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end
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