Solve 2021 Day 7 part 1 in elixir

garritfra · garritfra · commit 70eae774fac3 · 2021-12-07T17:04:26.000+01:00
diff --git a/2021/Day7/Elixir/whales.ex b/2021/Day7/Elixir/whales.ex
@@ -0,0 +1,53 @@
+ExUnit.start()
+
+defmodule Whales do
+  def load_file(path) do
+    File.read!(path)
+    |> String.split(",", trim: true)
+    |> Enum.map(&Integer.parse/1)
+    |> Enum.map(&elem(&1, 0))
+  end
+
+  def distance_to(a, b), do: abs(a - b)
+
+  def find_cheapest_route(positions),
+    do: find_cheapest_route(positions, Enum.min(positions), nil)
+
+  def find_cheapest_route(positions, target, cheapest) do
+    if target == Enum.max(positions) + 1 do
+      cheapest
+    else
+      current =
+        if target == Enum.max(positions) + 1 do
+          cheapest
+        else
+          positions
+          |> Enum.map(fn position -> distance_to(position, target) end)
+          |> Enum.sum()
+        end
+
+      new_cheapest =
+        if current < cheapest do
+          current
+        else
+          cheapest
+        end
+
+      find_cheapest_route(positions, target + 1, new_cheapest)
+    end
+  end
+
+  @spec first() :: Integer
+  def first() do
+    positions = load_file("../input.txt")
+    find_cheapest_route(positions)
+  end
+
+  @spec second() :: Integer
+  def second() do
+  end
+end
+
+defmodule WhalesTest do
+  use ExUnit.Case
+end
diff --git a/2021/Day7/test.txt b/2021/Day7/test.txt
@@ -0,0 +1 @@
+16,1,2,0,4,2,7,1,2,14
