Day 1

lib/day1.ex

@@ -2,14 +2,48 @@ defmodule Aoc2023.Day1 do
   use Aoc2023
 
   def parse(input) do
-    input
+    fn (replacement) ->
+      input
+      |> String.split("\n")
+      |> Enum.map(replacement)
+      |> Enum.map(fn (line) -> 
+        line
+        |> String.to_charlist()
+        |> Enum.filter(&(?0 <= &1 && &1 <= ?9))
+        |> Enum.map(&(&1 - ?0))
+      end)
+      |> Enum.map(&[List.first(&1), List.last(&1)])
+      |> Enum.filter(fn (l) -> Enum.all?(l, &(&1 != nil)) end)
+      |> Enum.map(&Integer.undigits/1)
+      |> Enum.sum
+    end
   end
 
   def part1(input) do
-    nil
+    input.(fn line -> line end)
   end
 
-  def part2(input) do
-    nil
+  @numbers [
+    "one",
+    "two",
+    "three",
+    "four",
+    "five",
+    "six",
+    "seven",
+    "eight",
+    "nine",
+  ]
+
+  defp replacements(line) do
+    line
+    |> String.replace(@numbers, fn (n) -> Integer.to_string(Enum.find_index(@numbers, &(&1 == n)) + 1) <> String.slice(n, 1..String.length(n)) end)
   end
+
+  defp replacements_rec(line) do
+    if replacements(line) == line, do: line, else: replacements_rec(replacements(line))
+  end
+  def part2(input) do
+    input.(&replacements_rec/1)
+ end
 end