96 lines
2.4 KiB
Elixir
96 lines
2.4 KiB
Elixir
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#!/usr/bin/env elixir
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defmodule Day5 do
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def part1({seeds, maps}) do
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seeds
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|> Enum.map(fn seed -> Enum.reduce(maps, seed, &lookup/2) end)
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|> Enum.min()
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end
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def lookup([], item), do: item
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def lookup([{source, dest} | rest], item) do
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if item in source do
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dest + item - source.first
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else
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lookup(rest, item)
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end
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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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# dest range start
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# source range start
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# length
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# no map = same number
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# could brute force it by building a map
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# but the ranges are huge, so that won't work
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# actually need to find if in a range
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# given a source
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# 1) check if it's in a range
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# 2) if it is, follow the rule, otherwise same number
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# 3) follow path
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# well it's mlogn but it should work?
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# store a list of ranges
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# check each seed to see if it's in the range, if it is, follow it, if not, name number
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# we could binsearch the range but let's just do it linear for now, there aren't many seeds
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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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["seeds: " <> seeds | maps] = String.split(input, "\n\n")
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seeds = seeds |> String.split() |> Enum.map(&String.to_integer/1)
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maps =
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Enum.map(maps, fn line ->
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[_header, _map | items] = String.split(line)
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items
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|> Enum.map(&String.to_integer/1)
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|> Enum.chunk_every(3)
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|> Enum.map(fn [dest, source, offset] ->
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{source..(source + offset), dest}
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end)
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end)
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{seeds, maps}
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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 day5.exs input_filename")
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end
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end
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# Day5.run()
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