104 lines
2.9 KiB
Elixir
104 lines
2.9 KiB
Elixir
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defmodule AOC.Day12 do
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use AOC.Day, day: 12, input: "example"
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# use AOC.Day, day: 12
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def parse_input(lines) do
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Enum.map(lines, fn line ->
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[conditions, groups] = String.split(line, " ")
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conditions = String.to_charlist(conditions)
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groups =
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groups
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|> String.split(",")
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|> Enum.map(&String.to_integer/1)
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{conditions, groups}
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end)
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end
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def possible_unknown_spring_conditions(unknown_spring_count) when unknown_spring_count == 0,
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do: [[]]
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def possible_unknown_spring_conditions(unknown_spring_count) do
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next_list = possible_unknown_spring_conditions(unknown_spring_count - 1)
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Enum.map(next_list, &[true | &1]) ++ Enum.map(next_list, &[false | &1])
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end
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def apply_spring_configuration([], []), do: []
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def apply_spring_configuration([?. | conditions], spring_configuration) do
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[?. | apply_spring_configuration(conditions, spring_configuration)]
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end
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def apply_spring_configuration([?# | conditions], spring_configuration) do
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[?# | apply_spring_configuration(conditions, spring_configuration)]
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end
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def apply_spring_configuration([?? | conditions], [true | spring_configuration]) do
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[?. | apply_spring_configuration(conditions, spring_configuration)]
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end
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def apply_spring_configuration([?? | conditions], [false | spring_configuration]) do
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[?# | apply_spring_configuration(conditions, spring_configuration)]
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end
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def valid_spring_conditions?(conditions, []) do
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not Enum.member?(conditions, ?#)
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end
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def valid_spring_conditions?([?. | conditions], groups) do
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valid_spring_conditions?(conditions, groups)
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end
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def valid_spring_conditions?(conditions, [count | groups]) do
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{left, right} = Enum.split(conditions, count)
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length(left) == count and Enum.all?(left, &(&1 == ?#)) and
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(length(right) == 0 or hd(right) == ?.) and valid_spring_conditions?(right, groups)
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end
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def generate_arrangements(conditions, groups) do
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unknown_spring_count = Enum.count(conditions, &(&1 == ??))
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possible_unknown_spring_conditions(unknown_spring_count)
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|> Stream.map(fn spring_configuration ->
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apply_spring_configuration(conditions, spring_configuration)
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end)
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|> Stream.filter(fn possible_conditions ->
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valid_spring_conditions?(possible_conditions, groups)
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end)
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# |> Enum.to_list()
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end
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def calculate_arrangement_counts(input, duplicates \\ 1) do
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input
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|> Enum.map(fn {conditions, groups} ->
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conditions =
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conditions
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|> List.duplicate(duplicates)
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|> Enum.intersperse(~c"?")
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|> List.flatten()
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groups =
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groups
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|> List.duplicate(duplicates)
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|> List.flatten()
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generate_arrangements(conditions, groups)
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end)
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|> Enum.map(&Enum.count/1)
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|> Enum.sum()
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end
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def part1(input) do
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calculate_arrangement_counts(input)
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end
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def part2(input) do
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calculate_arrangement_counts(input, 5)
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end
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end
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# NOTE TO SELF: memoize the brute force...
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