67 lines
1.6 KiB
Elixir
67 lines
1.6 KiB
Elixir
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#!/usr/bin/env elixir
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defmodule Day1 do
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def part1({list1, list2}) do
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list1 = Enum.sort(list1)
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list2 = Enum.sort(list2)
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distances(list1, list2) |> Enum.sum()
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end
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def distances([], []), do: []
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def distances([h1 | t1], [h2 | t2]), do: [abs(h1 - h2) | distances(t1, t2)]
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def part2({list1, list2}) do
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frequencies = Enum.frequencies(list2)
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Enum.reduce(list1, 0, fn item, count -> count + item * Map.get(frequencies, item, 0) end)
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end
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def input do
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with [input_filename] <- System.argv(),
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{:ok, input} <- File.read(input_filename) do
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integers =
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input
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|> String.split([" ", "\n"], trim: true)
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|> Enum.map(&String.to_integer/1)
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list1 = Enum.take_every(integers, 2)
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list2 = Enum.take_every(tl(integers), 2)
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{list1, list2}
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else
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_ -> :error
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end
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end
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#######################
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# HERE BE BOILERPLATE #
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#######################
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def run do
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case input() do
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:error -> print_usage()
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input -> run_parts_with_timer(input)
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end
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end
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defp run_parts_with_timer(input) do
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run_with_timer(1, fn -> part1(input) end)
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run_with_timer(2, fn -> part2(input) end)
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end
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defp run_with_timer(part, fun) do
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{time, result} = :timer.tc(fun)
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IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
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IO.puts("#{inspect(result)}\n")
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end
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defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
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defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
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defp format_time(μsec), do: "#{μsec / 1_000_000}s"
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defp print_usage do
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IO.puts("Usage: elixir day1.exs input_filename")
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end
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end
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Day1.run()
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