elixir - add day 11 solutions

elixir/lib/Y2022/day11.ex

@@ -0,0 +1,120 @@
+defmodule MonkeyUtil do
+  def parse_op(z, s) do
+    "Operation: new = " <> z, s -> parse_op(z, s)
+    "old " <> z, s -> parse_op(z, [:old | s])
+    "old" <> z, s -> parse_op(z, [:old | s])
+    "+ " <> z, s -> parse_op(z, [:plus | s])
+    "- " <> z, s -> parse_op(z, [:minus | s])
+    "* " <> z, s -> parse_op(z, [:mul | s])
+    "/ " <> z, s -> parse_op(z, [:div | s])
+    "", _, s -> s |> Enum.reverse()
+    n, s ->
+      [a | b] = String.split( n, " ")
+      a = String.trim(a) |> String.to_integer()
+      parse_op(b |> Enum.join(" "), [a | s])
+  end
+
+  def subs(b, a), do: if b == :old, do: a, else: b
+  def resolve_stack(x, y) do
+    (fn
+    old, [a, :plus, b] -> subs(a, old) + subs(b, old)
+    old, [a, :minus, b] -> subs(a, old) - subs(b, old)
+    old, [a, :mul, b] -> subs(a, old) * subs(b, old)
+    old, [a, :div, b] -> subs(a, old) / subs(b, old) end).(x, y)
+  end
+end
+
+defmodule Monkey do
+  defstruct id: nil, items: nil, op: nil, mod: nil, if_true: nil, if_false: nil, inspections: 0
+end
+
+defmodule MonkeyMachine do
+  def load(instructions) do
+    {barrel, _} = for instruction <- instructions, reduce: {%{}, nil} do
+      {barrel, monkey} ->
+        (fn
+          {:break} ->
+          {barrel |> Map.put(monkey.id, monkey), nil}
+          {:add_monkey, id} -> {barrel, %Monkey{id: id}}
+          {:starting_items, i} -> {barrel, %{monkey | items: i }}
+          {a, o} -> {barrel, %{monkey | a => o }}
+        end).(instruction)
+    end
+
+    barrel
+  end
+
+  def run(barrel, :part1) do
+    run(barrel, 0, (Map.keys(barrel) |> Enum.count()) - 1)
+  end
+
+  def run(barrel, :part2) do
+    run(barrel, 0, (Map.keys(barrel) |> Enum.count()) - 1, Map.values(barrel) |> Stream.map(&(&1.mod)) |> Enum.product())
+  end
+
+  defp run(barrel, i, n) when i > n, do: barrel
+  defp run(barrel, id, n) do
+    monkey = Map.get(barrel, id)
+    barrel = for item <- monkey.items, reduce: barrel do
+      b ->
+        item = div(monkey.op.(item), 3)
+        dest = if rem(item, monkey.mod) == 0, do: monkey.if_true, else: monkey.if_false
+
+        b
+          |> Map.update!(dest, fn d -> %{d | items: [item | d.items]} end)
+          |> Map.update!(id, fn m -> Map.update!(m, :inspections, &(&1 + 1)) end)
+        end |> Map.update!(id, fn m -> %{m | items: []} end)
+
+    run(barrel, id + 1, n)
+  end
+
+  defp run(barrel, i, n, _) when i > n, do: barrel
+  defp run(barrel, id, n, m) do
+    monkey = Map.get(barrel, id)
+    barrel = for item <- monkey.items, reduce: barrel do
+      b ->
+        r = rem(monkey.op.(item), m)
+        item = if r == 0, do: m, else: r
+        dest = if rem(r, monkey.mod) == 0, do: monkey.if_true, else: monkey.if_false
+
+        b
+          |> Map.update!(dest, fn d -> %{d | items: [item | d.items]} end)
+          |> Map.update!(id, fn m -> Map.update!(m, :inspections, &(&1 + 1)) end)
+        end |> Map.update!(id, fn m -> %{m | items: []} end)
+
+    run(barrel, id + 1, n, m)
+  end
+end
+
+defmodule MonkeySolver do
+  # part := :part1 || :part2
+  def solve(input, part) do
+    barrel = input
+    |> String.split("\n")
+    |> Stream.map(&String.trim/1)
+    |> Enum.map(
+      fn
+        "Monkey " <> z -> {:add_monkey, z |> String.split(":") |> Enum.at(0) |> String.to_integer()}
+        "Starting items: " <> i -> {:starting_items, i |> String.split(",", trim: true) |> Enum.map(&String.to_integer(String.trim(&1)))}
+        "Operation: " <> _ = u -> {:op, fn o -> MonkeyUtil.resolve_stack(o, MonkeyUtil.parse_op(u, [])) end}
+        "Test: divisible by " <> n -> {:mod, String.to_integer(n)}
+        "If true: throw to monkey " <> n -> {:if_true, String.to_integer(n)}
+        "If false: throw to monkey " <> n -> {:if_false, String.to_integer(n)}
+        "" -> {:break}
+        u -> u
+      end
+    )
+    |> MonkeyMachine.load()
+
+    iterations = if part == :part1, do: 20, else: 10_000 end
+
+    for _ <- 1..iterations, reduce: barrel do
+      b -> MonkeyMachine.run(b, part)
+    end
+    |> Map.values()
+    |> Stream.map(&(&1.inspections))
+    |> Enum.sort(:desc)
+    |> Enum.take(2)
+    |> Enum.product()
+  end
+end

elixir/test/2022/day11_test.exs

@@ -0,0 +1,35 @@
+defmodule AoC.Y2022.Day11.Test do
+  use ExUnit.Case
+
+  test "AoC.Y2022.Day11" do
+    assert MonkeySolver.solve("""
+      Monkey 0:
+        Starting items: 79, 98
+        Operation: new = old * 19
+        Test: divisible by 23
+          If true: throw to monkey 2
+          If false: throw to monkey 3
+
+      Monkey 1:
+        Starting items: 54, 65, 75, 74
+        Operation: new = old + 6
+        Test: divisible by 19
+          If true: throw to monkey 2
+          If false: throw to monkey 0
+
+      Monkey 2:
+        Starting items: 79, 60, 97
+        Operation: new = old * old
+        Test: divisible by 13
+          If true: throw to monkey 1
+          If false: throw to monkey 3
+
+      Monkey 3:
+        Starting items: 74
+        Operation: new = old + 3
+        Test: divisible by 17
+          If true: throw to monkey 0
+          If false: throw to monkey 1
+      """, :part1) == 10605
+  end
+end