Day 8 Part 1

2020/day8/day8.ex

@@ -0,0 +1,40 @@
+defmodule Day8 do
+  defp read_input do
+    Path.expand('input', Path.dirname(__ENV__.file))
+    |> File.read!()
+  end
+
+  defp parse_program(text) do
+    String.split(String.trim(text), "\n")
+    |> Enum.map(fn line ->
+      [op, val] = String.split(line)
+      {op, String.to_integer(val)}
+    end)
+  end
+
+  defp tick(program, pc, acc) do
+    case Enum.at(program, pc) do
+      {"nop", _} -> {pc + 1, acc}
+      {"acc", int} -> {pc + 1, acc + int}
+      {"jmp", int} -> {pc + int, acc}
+    end
+  end
+
+  defp find_loop(program, pc, acc, history) do
+    {next_pc, next_acc} = tick(program, pc, acc)
+    count = Map.get(history, next_pc, 0)
+
+    if count > 0 do
+      acc
+    else
+      find_loop(program, next_pc, next_acc, Map.put(history, next_pc, count + 1))
+    end
+  end
+
+  def part1 do
+    program = parse_program(read_input())
+    find_loop(program, 0, 0, %{})
+  end
+end
+
+Day8.part1() |> IO.inspect()