60 lines
1.5 KiB
Elixir
60 lines
1.5 KiB
Elixir
defmodule Day2 do
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@moduledoc """
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Documentation for `Day2`.
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"""
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require Integer
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def start(_type, _args) do
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input_file = File.read("input/day2.txt")
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IO.puts("Part 1: #{Day2.part1(elem(input_file, 1))}")
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IO.puts("Part 2: #{Day2.part2(elem(input_file, 1))}")
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opts = [strategy: :one_for_one, name: A.Supervisor]
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Supervisor.start_link([], opts)
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end
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def part1(input) do
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eval(input, &Day2.is_invalid_id_pt1/1)
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end
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def part2(input) do
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eval(input, &Day2.is_invalid_id_pt2/1)
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end
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def eval(input, id_checker) do
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for range <- String.split(input, ",") do
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[from, to] = String.split(range, "-") |> Enum.map(fn s -> String.to_integer(s) end)
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eval_range(from, to, id_checker)
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end
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|> Enum.sum()
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end
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def eval_range(from, to, id_checker) do
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Enum.filter(from..to, fn x -> id_checker.(x) end) |> Enum.sum()
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end
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def is_invalid_id_pt1(id) do
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digit_count = Enum.count(Integer.digits(id))
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power = 10 ** div(digit_count, 2)
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# IO.inspect {id, digit_count, power, div(id, power), rem(id, power)}
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Integer.is_even(digit_count) && div(id, power) == rem(id, power)
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end
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def is_invalid_id_pt2(id) do
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if id <= 10 do
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false
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else
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id_digits = Integer.digits(id)
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digit_count = Enum.count(id_digits)
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res =
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Enum.any?(1..div(digit_count, 2), fn pattern_size ->
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sections = Enum.chunk_every(id_digits, pattern_size)
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Enum.all?(Enum.drop(sections, 1), fn x -> x == Enum.at(sections, 0) end)
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end)
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res
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end
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end
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end
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