35 lines
961 B
Elixir
35 lines
961 B
Elixir
defmodule Day7Part2 do
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@bag_spec ~r/\A(\d) (\w+ \w+).*\z/
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def run do
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File.read!("input")
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|> input_to_tree()
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|> count_descendants("shiny gold")
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|> IO.puts()
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end
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def count_descendants(tree, name) do
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Enum.reduce(tree[name], 0, fn {size, child_name}, count ->
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count + size + size * count_descendants(tree, child_name)
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end)
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end
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# %{"shiny gold" => [{5, "pale brown"}, {2, "light red"}, {3, "drab lime"}]}
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def input_to_tree(input) do
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input
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|> String.split(".\n", trim: true)
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|> Enum.map(&String.split(&1, " bags contain "))
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|> Map.new(fn [parent, child_spec] -> {parent, parse_children(child_spec)} end)
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end
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def parse_children("no other bags"), do: []
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def parse_children(child_spec) do
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child_spec
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|> String.split(", ")
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|> Enum.map(&Regex.run(@bag_spec, &1, capture: :all_but_first))
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|> Enum.map(fn [count, type] -> {String.to_integer(count), type} end)
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end
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end
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Day7Part2.run()
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