32 lines
845 B
Elixir
32 lines
845 B
Elixir
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defmodule Day10Part2 do
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def run do
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File.read!("input")
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|> String.split("\n", trim: true)
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|> Enum.map(&String.to_integer/1)
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|> count_arrangements()
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|> IO.puts()
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end
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def count_arrangements(list), do: count_arrangements(%{0 => 1}, [0 | Enum.sort(list)])
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def count_arrangements(arrs_to, [last]), do: arrs_to[last]
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def count_arrangements(arrs_to, [current | rest]) do
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rest
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|> Enum.take(3)
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|> count_reachable(current, arrs_to)
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|> count_arrangements(rest)
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end
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def count_reachable([], _a, arrs_to), do: arrs_to
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def count_reachable([b | rest], a, arrs_to) when b - a <= 3 do
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arrs_to = Map.update(arrs_to, b, arrs_to[a], &(&1 + arrs_to[a]))
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count_reachable(rest, a, arrs_to)
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end
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def count_reachable([_b | rest], a, arrs_to), do: count_reachable(rest, a, arrs_to)
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end
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Day10Part2.run()
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