Day 2: Inventory Management System - Advent of Code 2018

I did the Advent of Code 2018 day 2 challenge in Elixir! Parts one and two are as follows:

defmodule Day2 do
  def checksum(input) do
    {two, three} =
      input
      |> read_input()
      |> Enum.reduce({0, 0}, fn line, {appears_two_times, appears_three_times} ->
        {two_times, three_times, _} =
          line
          |> String.graphemes()
          |> Enum.group_by(& &1)
          |> get_checksum_values()

        {appears_two_times + two_times, appears_three_times + three_times}
      end)

    two * three
  end

  def differ(input) do
    lines = input |> read_input()

    # length(diff) == 4 # [eq: "_", del: "_", ins: "_", eq: "_"]
    for line1 <- lines,
        line2 <- lines,
        line1 != line2,
        diff = String.myers_difference(line1, line2),
        length(diff) == 4 do
      diff
      |> Keyword.get_values(:eq)
      |> Enum.join()
    end
    |> Enum.uniq()
  end

  defp read_input(input) do
    input
    |> File.read!()
    |> String.split("\n", trim: true)
  end

  defp get_checksum_values(groups) do
    Enum.reduce(groups, {0, 0, MapSet.new()}, fn {_key, chars},
                                                 {two_times, three_times, seen} = acc ->
      value = length(chars)

      if MapSet.member?(seen, value) do
        acc
      else
        new_seen = MapSet.put(seen, value)

        case value do
          2 -> {two_times + 1, three_times, new_seen}
          3 -> {two_times, three_times + 1, new_seen}
          _ -> {two_times, three_times, new_seen}
        end
      end
    end)
  end
end

:aoc2018 |> :code.priv_dir() |> Path.join("day2.txt") |> Day2.checksum()
:aoc2018 |> :code.priv_dir() |> Path.join("day2.txt") |> Day2.differ()

 
Author

Simon Escobar Benitez

Colombian Software Engineer (Erlang Solutions)

Upcoming conferences

Start booking your calendar with more Code Sync conferences happening across the globe. We will be slowly releasing more dates, in the meantime here is what we’ve planned already:

All conferences

ARTICLES: 5

Day 10: The Stars Align - Advent of Code 2018
Simon Escobar Benitez

I did the Advent of Code 2018 day 10 challenge in Elixir! Parts one and two are as follows:

READ MORE
  • Elixir
  • Advent of Code
Day 5: Alchemical Reduction - Advent of Code 201
Simon Escobar Benitez

I did the Advent of Code 2018 day 5 challenge in Elixir! Parts one and two are as follows:

READ MORE
  • Elixir
  • Advent of Code
Day 4: Repose Record - Advent of Code 2018
Simon Escobar Benitez

I did the Advent of Code 2018 day 4 challenge in Elixir! Parts one and two are as follows:

READ MORE
  • Elixir
  • Advent of Code
Day 3: No matter how you slice it - Advent of Code 2018
Simon Escobar Benitez

I did the Advent of Code 2018 day 3 challenge in Elixir! Parts one and two are as follows:

READ MORE
  • Elixir
  • Advent of Code
Day 1: Chronal Calibration - Advent of Code 2018
Simon Escobar Benitez

Advent of Code 2018 - Day 1 solution in Elixir! #AdventOfBEAM

READ MORE
  • Elixir
  • Advent of Code