day 03

Mix.install([
  {:kino, "~> 0.12.2"}
])

Section

example = Kino.Input.textarea("paste")

defmodule Helper do
  def solver(total_lines, total_cols, grid, {right, down}) do
    Enum.reduce_while(
      0..total_lines,
      %{
        col: 0,
        row: 0,
        grid: grid,
        trees: 0
      },
      fn _,
         %{
           col: col,
           row: row,
           grid: grid,
           trees: trees
         } = acc ->
        cond do
          row >= total_lines or col >= total_cols ->
            {:halt, trees}

          elem(grid, row) |> elem(col) == "#" ->
            {:cont, %{acc | trees: trees + 1, col: col + right, row: row + down}}

          true ->
            {:cont, %{acc | col: col + right, row: row + down}}
        end
      end
    )
  end
end

Part 01

lines =
  example
  |> Kino.Input.read()
  |> String.split("\n", trim: true)

grid =
  Enum.map(lines, fn line ->
    String.duplicate(line, Enum.count(lines))
    |> String.split("", trim: true)
    |> List.to_tuple()
  end)
  |> List.to_tuple()

total_cols = tuple_size(elem(grid, 0))
total_lines = lines |> Enum.count()
Helper.solver(total_lines, total_cols, grid, {3, 1})

Part 02

slopes = [{1, 1}, {3, 1}, {5, 1}, {7, 1}, {1, 2}]

Enum.reduce(slopes, 1, fn slope, acc ->
  Helper.solver(total_lines, total_cols, grid, slope) * acc
end)