105 lines
2.3 KiB
Elixir
105 lines
2.3 KiB
Elixir
import AOC
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aoc 2015, 18 do
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def input() do
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lists =
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input_string()
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|> String.split("\n", trim: true)
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|> Enum.map(fn line ->
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line
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|> String.split("", trim: true)
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|> Enum.map(&decode_state/1)
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|> Enum.with_index(1)
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end)
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|> Enum.with_index(1)
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for {row, i} <- lists, {cell, j} <- row, into: %{} do
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{{i, j}, cell}
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end
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end
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def decode_state("#"), do: :on
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def decode_state("."), do: :off
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def encode_state(:on), do: "#"
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def encode_state(:off), do: :off
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def n({i, j}), do: {i - 1, j}
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def e({i, j}), do: {i, j + 1}
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def s({i, j}), do: {i + 1, j}
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def w({i, j}), do: {i, j - 1}
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def ne(pos), do: pos |> n() |> e()
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def se(pos), do: pos |> s() |> e()
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def sw(pos), do: pos |> s() |> w()
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def nw(pos), do: pos |> n() |> w()
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def neighbors(map, pos) do
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[&n/1, &ne/1, &e/1, &se/1, &s/1, &sw/1, &w/1, &nw/1]
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|> Enum.map(&apply(&1, [pos]))
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|> Enum.map(&Map.get(map, &1, :off))
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|> Enum.frequencies()
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end
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def tick(map) do
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for {pos, cell} <- map, into: %{} do
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next_cell =
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case {cell, neighbors(map, pos)} do
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{:on, %{on: on}} when on in [2, 3] -> :on
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{:on, _} -> :off
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{:off, %{on: 3}} -> :on
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{:off, _} -> :off
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end
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{pos, next_cell}
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end
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end
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def tick_with_corners_on(map) do
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for {pos, cell} <- map, into: %{} do
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if pos in [{1, 1}, {1, 100}, {100, 1}, {100, 100}] do
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{pos, :on}
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else
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next_cell =
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case {cell, neighbors(map, pos)} do
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{:on, %{on: on}} when on in [2, 3] -> :on
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{:on, _} -> :off
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{:off, %{on: 3}} -> :on
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{:off, _} -> :off
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end
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{pos, next_cell}
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end
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end
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end
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def p1 do
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start = input()
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finish =
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for _ <- 1..100, reduce: start do
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curr -> tick(curr)
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end
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finish
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|> Map.values()
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|> Enum.count(&(&1 == :on))
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end
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def p2 do
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start =
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input()
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|> Map.put({1, 1}, :on)
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|> Map.put({1, 100}, :on)
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|> Map.put({100, 1}, :on)
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|> Map.put({100, 100}, :on)
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finish =
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for _ <- 1..100, reduce: start do
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curr -> tick_with_corners_on(curr)
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end
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finish
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|> Map.values()
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|> Enum.count(&(&1 == :on))
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end
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end
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