81 lines
1.8 KiB
Elixir
Executable file
81 lines
1.8 KiB
Elixir
Executable file
#!/usr/bin/env elixir
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defmodule Day13 do
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defmodule Machine do
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defstruct [:a, :b, :prize]
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end
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def part1(input) do
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input
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# these are equivalent linear equations
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# know how to do it algebraically, but not algorithmically
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# e.g. for first example
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#
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# 94a + 22b - 8400 = 34a + 67b - 5400
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# 94a + 22b - 3000 = 34a + 67b
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# 60a + 22b - 3000 = 67b
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# 60a - 3000 = 45b
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# 4a - 200 = 3b
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# a = 3/4b + 50
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# 34(3/4b + 50) + 67b - 5400 = 0
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# 25.5b + 1700 + 67b - 5400 = 0
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# 92.5b = 3700
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# b = 40
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# 34a + 67(40) = 5400
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# 34a + 2680 = 5400
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# 34a = 2720
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# a = 80
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end
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def part2(_input) do
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:ok
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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\n")
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|> Enum.map(fn machine ->
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machine
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|> String.split(["+", ",", "=", "\n"], trim: true)
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|> tl()
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|> Enum.take_every(2)
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|> Enum.map(&String.to_integer/1)
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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 day13.exs input_filename")
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end
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end
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# Day13.run()
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