103 lines
2.7 KiB
Elixir
103 lines
2.7 KiB
Elixir
defmodule Marble do
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defstruct [:cw, :ccw]
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end
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defmodule Game do
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defstruct [:current, :next, :circle, :players, :active, :scores, :marbles]
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def start(players, marbles) do
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game = %Game{
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current: 0,
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next: 1,
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circle: %{0 => %Marble{ccw: 0, cw: 0}},
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players: players,
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active: 1,
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scores: Map.new(1..players, &{&1, 0}),
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marbles: marbles
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}
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play(game)
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end
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def next_turn(%Game{next: next, marbles: marbles} = game) when next > marbles do
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game.scores |> Map.values() |> Enum.max()
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end
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def next_turn(%Game{players: players, active: active} = game) do
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next = active + 1
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next = if next <= players, do: next, else: 1
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play(%Game{game | active: next})
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end
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def insert(circle, val, ccw, cw) do
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circle
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|> Map.put(val, %Marble{ccw: ccw, cw: cw})
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|> Map.update!(ccw, &%Marble{&1 | cw: val})
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|> Map.update!(cw, &%Marble{&1 | ccw: val})
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end
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def remove(circle, val, ccw, cw) do
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circle
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|> Map.delete(val)
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|> Map.update!(ccw, &%Marble{&1 | cw: cw})
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|> Map.update!(cw, &%Marble{&1 | ccw: ccw})
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end
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def find_remove(cw, circle, 1) do
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remove = circle[cw].ccw
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ccw = circle[remove].ccw
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{remove, ccw, cw}
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end
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def find_remove(current, circle, dec) do
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find_remove(circle[current].ccw, circle, dec - 1)
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end
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def play(%Game{current: current, next: val, circle: circle} = game) when rem(val, 23) == 0 do
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# Find and remove the item 7 items over
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{remove, ccw, cw} = find_remove(current, circle, 7)
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circle = remove(circle, remove, ccw, cw)
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# Update the player's score
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scores = Map.update!(game.scores, game.active, &(&1 + val + remove))
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game = %Game{game | current: cw, next: val + 1, circle: circle, scores: scores}
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next_turn(game)
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end
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def play(%Game{current: current, next: val, circle: circle} = game) do
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one = circle[current].cw
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two = circle[one].cw
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game = %Game{game | current: val, next: val + 1, circle: insert(circle, val, one, two)}
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next_turn(game)
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end
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end
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defmodule Day9 do
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def part1 do
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input = File.read!("input")
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pattern = ~r/(\d+) players; last marble is worth (\d+) points/
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[players, marbles] =
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Regex.run(pattern, input, capture: :all_but_first)
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|> Enum.map(&String.to_integer/1)
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Game.start(players, marbles)
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end
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# Probably supposed to make this more efficient, but it still runs in 30 seconds...
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def part2 do
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input = File.read!("input")
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pattern = ~r/(\d+) players; last marble is worth (\d+) points/
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[players, marbles] =
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Regex.run(pattern, input, capture: :all_but_first)
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|> Enum.map(&String.to_integer/1)
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Game.start(players, marbles * 100)
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end
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end
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IO.puts(Day9.part1())
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IO.puts(Day9.part2())
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