Day 1

lib/day1.ex

@@ -2,14 +2,48 @@ defmodule Aoc2023.Day1 do
   use Aoc2023
 
   def parse(input) do
+    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
 
+  @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
-    nil
+    input.(&replacements_rec/1)
  end
 end

tests/day1/1

@@ -0,0 +1,4 @@
+1abc2
+pqr3stu8vwx
+a1b2c3d4e5f
+treb7uchet

tests/day1/1.1

@@ -0,0 +1 @@
+142

tests/day1/1.2

@@ -0,0 +1 @@
+142

tests/day1/2

@@ -0,0 +1,7 @@
+two1nine
+eightwothree
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen

tests/day1/2.1

@@ -0,0 +1 @@
+209

tests/day1/2.2

@@ -0,0 +1 @@
+281