(wip) 2024 day 14

2024/lib/2024/14.ex

@@ -0,0 +1,62 @@
+import AOC
+
+aoc 2024, 14 do
+  @example_bounds
+  # @bounds @example_bounds
+  # @real_bounds {101, 103}
+
+  def p1(input) do
+    robots =
+      input
+      |> read_robots()
+      |> Stream.iterate(fn robots ->
+        Enum.map(robots, &move_robot(&1, @bounds))
+      end)
+      |> Enum.at(100)
+      |> Enum.frequencies_by(&elem(&1, 0))
+
+    render(robots, @bounds)
+
+    :ok
+  end
+
+  def p2(_input) do
+  end
+
+  defp move_robot({{x, y}, {vx, vy} = velocity}, {max_x, max_y}) do
+    x_next = wrap_value(x + vx, max_x)
+    y_next = wrap_value(y + vy, max_y)
+
+    {{x_next, y_next}, velocity}
+  end
+
+  defp wrap_value(v, max) do
+    if v < 0 do
+      max + v
+    else
+      rem(v, max)
+    end
+  end
+
+  defp render(robots, {max_x, max_y}) do
+    for y <- 0..max_y do
+      line =
+        for x <- 0..max_x, into: "" do
+          "#{Map.get(robots, {x, y}, ".")}"
+        end
+
+      IO.puts(line)
+    end
+  end
+
+  ## input
+
+  defp read_robots(input) do
+    ~r/p=(\d+),(\d+) v=(-?\d+),(-?\d+)/
+    |> Regex.scan(input, capture: :all_but_first)
+    |> Enum.map(fn nums ->
+      [px, py, vx, vy] = Enum.map(nums, &String.to_integer/1)
+      {{px, py}, {vx, vy}}
+    end)
+  end
+end