Day 18. Going to come back to day 17... maybe

day18/main.exs

@@ -0,0 +1,149 @@
+defmodule Day18 do
+  def run do
+    map_list =
+      File.read!("data.txt")
+      |> String.trim()
+      |> String.split("\n")
+      |> Enum.map(fn line -> String.split(line, ",") |> Enum.map(&String.to_integer/1) end)
+
+    height = 71
+    width = 71
+
+    map_list1 = Enum.take(map_list, 1024)
+
+    map1 =
+      Enum.reduce(0..(height - 1), %{}, fn row, acc ->
+        Enum.reduce(0..(width - 1), acc, fn col, acc2 ->
+          char = if Enum.member?(map_list1, [col, row]), do: :wall, else: :empty
+          Map.put(acc2, {col, row}, char)
+        end)
+      end)
+
+    start = {0, 0}
+    dest = {width - 1, height - 1}
+
+    # create a map of visited nodes an a queue
+    visited = %{start => 100_000_000}
+    q = :queue.from_list([{start, 0, [{0, 0}]}])
+
+    {_path, shortest} = walk(map1, q, dest, visited, [], 100_000_000_000, width, height)
+    dbg(shortest)
+
+    part2 =
+      Enum.reduce(1024..length(map_list), nil, fn idx, acc ->
+        dbg(idx)
+
+        if !is_nil(acc) do
+          # exit early, we already found the coord
+          acc
+        else
+          # take the first N coords
+          map_list = Enum.take(map_list, idx)
+
+          # generate a new map with that many blocks fallen
+          map =
+            Enum.reduce(0..(height - 1), %{}, fn row, acc ->
+              Enum.reduce(0..(width - 1), acc, fn col, acc2 ->
+                char = if Enum.member?(map_list, [col, row]), do: :wall, else: :empty
+                Map.put(acc2, {col, row}, char)
+              end)
+            end)
+
+          start = {0, 0}
+          dest = {width - 1, height - 1}
+
+          # create a map of visited nodes an a queue
+          visited = %{start => 100_000_000}
+          q = :queue.from_list([{start, 0, [{0, 0}]}])
+
+          res = walk(map, q, dest, visited, [], 100_000_000_000, width, height)
+          dbg(res)
+
+          if is_nil(res) do
+            List.last(map_list)
+          else
+            nil
+          end
+        end
+      end)
+
+    dbg(part2)
+  end
+
+  defp walk(map, q, {dx, dy} = dest, visited, paths, shortest_path, width, height) do
+    # dequeue the node with the lowest distnce
+    # no priority queue, so just find the lowest one and delete it from the queue
+    ql = :queue.to_list(q)
+
+    if length(ql) == 0 do
+      nil
+    else
+      lowest = Enum.min_by(ql, fn {_, dist, _} -> dist end)
+      {{x, y}, dist, path} = lowest
+      new_q = :queue.delete(lowest, q)
+
+      # if we reached the destination
+      if x == dx and y == dy do
+        {path, dist}
+      else
+        dirs = [{1, 0}, {0, 1}, {-1, 0}, {0, -1}]
+
+        # find neighbors to enqueue
+        neighbors =
+          dirs
+          |> Enum.map(fn {dx, dy} -> {x + dx, y + dy} end)
+          |> Enum.map(fn key -> {key, Map.get(map, key, :empty)} end)
+          |> Enum.filter(fn {{x, y}, el} ->
+            el != :wall and x >= 0 and y >= 0 and x < width and y < height
+          end)
+          |> Enum.reject(fn {{nx, ny}, _el} -> Map.has_key?(visited, {nx, ny}) end)
+          |> Enum.reject(fn {{nx, ny}, _el} ->
+            Enum.any?(:queue.to_list(q), fn {pos, _, _} -> pos == {nx, ny} end)
+          end)
+          |> Enum.map(fn {key, _el} -> key end)
+
+        new_q2 =
+          Enum.reduce(neighbors, new_q, fn {nx, ny}, acc ->
+            :queue.in({{nx, ny}, dist + 1, [{x, y} | path]}, acc)
+          end)
+
+        new_visited = Map.put(visited, {x, y}, dist)
+        walk(map, new_q2, dest, new_visited, paths, shortest_path, width, height)
+      end
+    end
+  end
+
+  defp render(map, location \\ nil, visited \\ %{}) do
+    width = Map.keys(map) |> Enum.map(&elem(&1, 1)) |> Enum.max()
+    height = Map.keys(map) |> Enum.map(&elem(&1, 0)) |> Enum.max()
+
+    Enum.each(0..height, fn row ->
+      Enum.each(0..width, fn col ->
+        el = if Map.get(map, {col, row}, :wall) == :wall, do: "#", else: "."
+
+        visited? = Map.has_key?(visited, {col, row})
+
+        formatted =
+          if location == {col, row} do
+            IO.ANSI.format([:red_background, "@"])
+          else
+            if visited? do
+              IO.ANSI.format([:blue_background, el])
+            else
+              el
+            end
+          end
+
+        IO.write(formatted)
+      end)
+
+      IO.write("\n")
+    end)
+
+    IO.write("\n")
+
+    map
+  end
+end
+
+Day18.run()