73 lines
1.8 KiB
Elixir
73 lines
1.8 KiB
Elixir
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#!/usr/bin/env elixir
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defmodule Day2 do
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def part1(reports) do
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Enum.count(reports, &check_report/1)
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end
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def check_report([a, b | _]) when abs(b - a) not in [1, 2, 3], do: false
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def check_report([a, b | rest]), do: check_report([b | rest], b - a)
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def check_report([_], _dir), do: true
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def check_report([a, b | rest], dir) do
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new_dir = b - a
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if ((dir < 0 and new_dir < 0) or (dir > 0 and new_dir > 0)) and abs(new_dir) <= 3 do
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check_report([b | rest], new_dir)
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else
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false
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end
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end
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def part2(reports) do
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Enum.count(reports, fn report ->
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Enum.find_value(0..(length(report) - 1), false, fn dampen ->
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{_, dampened} = List.pop_at(report, dampen)
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check_report(dampened)
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end)
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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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input
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|> String.split("\n", trim: true)
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|> Enum.map(fn line -> line |> String.split() |> Enum.map(&String.to_integer/1) end)
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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 day2.exs input_filename")
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end
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end
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Day2.run()
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