solve 2023 11.2

2023/lib/2023/11.ex

@@ -3,6 +3,42 @@ import AOCHelpers
 
 aoc 2023, 11 do
   def p1(input) do
+    input
+    |> read_input()
+    |> calculate_distances()
+  end
+
+  def p2(input) do
+    input
+    |> read_input()
+    |> calculate_distances(1_000_000)
+  end
+
+  def calculate_distances({galaxies, empty_columns, empty_rows}, expansion \\ 2) do
+    distance = make_distance_fn(empty_rows, empty_columns, expansion)
+
+    for [a, b] <- combinations(galaxies, 2), reduce: 0 do
+      acc -> acc + distance.(a, b)
+    end
+  end
+
+  def make_distance_fn(expanded_rows, expanded_columns, expansion) do
+    fn {x_a, y_a}, {x_b, y_b} ->
+      x_dist = abs(x_b - x_a)
+      y_dist = abs(y_b - y_a)
+
+      x_range = to_range(x_a, x_b)
+      y_range = to_range(y_a, y_b)
+
+      expanded_x = Enum.count(expanded_columns, &(&1 in x_range))
+      expanded_y = Enum.count(expanded_rows, &(&1 in y_range))
+
+      x_dist - expanded_x + expanded_x * expansion + (y_dist - expanded_y) +
+        expanded_y * expansion
+    end
+  end
+
+  def read_input(input) do
     {grid, {x_bounds, y_bounds}} = to_grid(input)
 
     empty_columns =
@@ -16,29 +52,7 @@ aoc 2023, 11 do
       |> Enum.filter(&match?({_, "#"}, &1))
       |> Enum.map(&elem(&1, 0))
 
-    distance = make_distance_fn(empty_rows, empty_columns)
-
-    for [a, b] <- combinations(galaxies, 2), reduce: 0 do
-      acc -> acc + distance.(a, b)
-    end
-  end
-
-  def p2(_input) do
-  end
-
-  def make_distance_fn(expanded_rows, expanded_columns) do
-    fn {x_a, y_a}, {x_b, y_b} ->
-      x_dist = abs(x_b - x_a)
-      y_dist = abs(y_b - y_a)
-
-      x_range = to_range(x_a, x_b)
-      y_range = to_range(y_a, y_b)
-
-      expanded_x = Enum.count(expanded_columns, &(&1 in x_range))
-      expanded_y = Enum.count(expanded_rows, &(&1 in y_range))
-
-      x_dist + expanded_x + y_dist + expanded_y
-    end
+    {galaxies, empty_columns, empty_rows}
   end
 
   def row(grid, y, x_bounds) do

README.md

@@ -14,7 +14,7 @@
 1. [2020] **17/50** 🌟
 1. [2021] **43/50** 🌟
 1. [2022] **14/50** 🌟
-1. [2023] **16/50** 🌟
+1. [2023] **17/50** 🌟
 
 [2015]: ./2015
 [2017]: ./2017