2023 - Day 01

Mix.install([
  {:req, "~> 0.4.5"},
  {:kino_vega_lite, "~> 0.1.11"},
  {:vega_lite, "~> 0.1.8"}
])

alias VegaLite, as: Vl

day = 1

aoc_session = System.fetch_env!("LB_AOC_SESSION")
input_url = "https://adventofcode.com/2023/day/#{day}/input"
{:ok, %{body: input}} = Req.get(input_url, headers: [cookie: "session=#{aoc_session}"])

Part 1

test_input = """
1abc2
pqr3stu8vwx
a1b2c3d4e5f
treb7uchet
"""

input
|> String.split("\n", trim: true)
|> Enum.reduce(0, fn str, acc ->
  digits = str |> String.replace(~r/[^0-9]/, "") |> String.graphemes()
  val = "#{List.first(digits)}#{List.last(digits)}" |> String.to_integer()
  acc + val
end)

Part 2

test_input = """
two1nine
eightwothree
abcone2threexyz
xtwone3four
4nineeightseven2
zoneight234
7pqrstsixteen
"""

defmodule P2 do
  def last_digit(str) do
    {rest, _} = String.split_at(str, -1)
    last_char = str |> String.to_charlist() |> List.last()

    cond do
      String.ends_with?(str, "one") -> 1
      String.ends_with?(str, "two") -> 2
      String.ends_with?(str, "three") -> 3
      String.ends_with?(str, "four") -> 4
      String.ends_with?(str, "five") -> 5
      String.ends_with?(str, "six") -> 6
      String.ends_with?(str, "seven") -> 7
      String.ends_with?(str, "eight") -> 8
      String.ends_with?(str, "nine") -> 9
      last_char in ?1..?9 -> last_char - ?0
      :else -> last_digit(rest)
    end
  end

  def first_digit(str) do
    {_, rest} = String.split_at(str, 1)
    first_char = str |> String.to_charlist() |> List.first()

    cond do
      String.starts_with?(str, "one") -> 1
      String.starts_with?(str, "two") -> 2
      String.starts_with?(str, "three") -> 3
      String.starts_with?(str, "four") -> 4
      String.starts_with?(str, "five") -> 5
      String.starts_with?(str, "six") -> 6
      String.starts_with?(str, "seven") -> 7
      String.starts_with?(str, "eight") -> 8
      String.starts_with?(str, "nine") -> 9
      first_char in ?1..?9 -> first_char - ?0
      :else -> first_digit(rest)
    end
  end
end

defmodule P3 do
  @digits [
    {"one", 1},
    {"two", 2},
    {"three", 3},
    {"four", 4},
    {"five", 5},
    {"six", 6},
    {"seven", 7},
    {"eight", 8},
    {"nine", 9}
  ]

  # def foo(str) do

  #   Enum.find_value(@digits, fn {word, num} -> String.starts_with?(str, word) && num end)
  # end

  def foo("one" <> rest), do: 1
  def foo()

  def last_digit(str) do
    {rest, _} = String.split_at(str, -1)
    last_char = str |> String.to_charlist() |> List.last()

    cond do
      String.ends_with?(str, "one") -> 1
      String.ends_with?(str, "two") -> 2
      String.ends_with?(str, "three") -> 3
      String.ends_with?(str, "four") -> 4
      String.ends_with?(str, "five") -> 5
      String.ends_with?(str, "six") -> 6
      String.ends_with?(str, "seven") -> 7
      String.ends_with?(str, "eight") -> 8
      String.ends_with?(str, "nine") -> 9
      last_char in ?1..?9 -> last_char - ?0
      :else -> last_digit(rest)
    end
  end

  def first_digit(str) do
    {_, rest} = String.split_at(str, 1)
    first_char = str |> String.to_charlist() |> List.first()

    cond do
      String.starts_with?(str, "one") -> 1
      String.starts_with?(str, "two") -> 2
      String.starts_with?(str, "three") -> 3
      String.starts_with?(str, "four") -> 4
      String.starts_with?(str, "five") -> 5
      String.starts_with?(str, "six") -> 6
      String.starts_with?(str, "seven") -> 7
      String.starts_with?(str, "eight") -> 8
      String.starts_with?(str, "nine") -> 9
      first_char in ?1..?9 -> first_char - ?0
      :else -> first_digit(rest)
    end
  end
end

input
|> String.split("\n", trim: true)
|> Enum.reduce(0, fn str, acc ->
  val = "#{P2.first_digit(str)}#{P2.last_digit(str)}" |> String.to_integer()
  acc + val
end)