37 lines
1,011 B
Elixir
37 lines
1,011 B
Elixir
import AOC
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aoc 2021, 7 do
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use AOCHelpers
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def crabs(), do: input_number_list()
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def p1, do: cost_of_most_efficient_position(&Function.identity/1)
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def p2, do: cost_of_most_efficient_position(&(1 / 2 * &1 * (&1 + 1)))
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def total_fuel_cost_for_position(crab_freqs, pos, cost_fun) do
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crab_freqs
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|> Enum.reduce(0, fn {crab_pos, num_crab}, partial_cost ->
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linear_distance = abs(crab_pos - pos)
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partial_cost + num_crab * cost_fun.(linear_distance)
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end)
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end
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def cost_of_most_efficient_position(cost_fun) when is_function(cost_fun) do
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crab_positions = input_number_list()
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max_crab_position = Enum.max(crab_positions)
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crab_frequencies = Enum.frequencies(crab_positions)
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crab_frequencies
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|> cost_of_most_efficient_position(1..max_crab_position, cost_fun)
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end
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def cost_of_most_efficient_position(crab_freqs, range, cost_fun) do
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range
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|> Enum.map(&total_fuel_cost_for_position(crab_freqs, &1, cost_fun))
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|> Enum.min()
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|> trunc()
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end
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end
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