Your answer is freakishly similar to mine…
defmodule Day8Part2 do
def find_corrupted(instrs), do: find_corrupted(Map.to_list(instrs), instrs, :loop)
def find_corrupted(_rest, _instrs, {:terminated, acc}), do: acc
def find_corrupted([{idx, {op, arg}} | rest], instrs, :loop) do
result =
instrs
|> Map.put(idx, toggle_op(op, arg))
|> try_boot()
find_corrupted(rest, instrs, result)
end
def try_boot(instrs), do: try_boot(instrs, 0, 0, MapSet.new())
def try_boot(instrs, idx, acc, _seen) when idx == map_size(instrs), do: {:terminated, acc}
def try_boot(instrs, idx, acc, seen) do
if MapSet.member?(seen, idx) do
:loop
else
seen = MapSet.put(seen, idx)
{idx, acc} = execute(instrs[idx], idx, acc)
try_boot(instrs, idx, acc, seen)
end
end
def execute({"nop", _arg}, idx, acc), do: {idx + 1, acc}
def execute({"jmp", arg}, idx, acc), do: {idx + arg, acc}
def execute({"acc", arg}, idx, acc), do: {idx + 1, acc + arg}
def toggle_op("acc", arg), do: {"acc", arg}
def toggle_op("nop", arg), do: {"jmp", arg}
def toggle_op("jmp", arg), do: {"nop", arg}
def input_to_instrs(input) do
input
|> String.split("\n", trim: true)
|> Enum.map(&String.split/1)
|> Enum.with_index()
|> Map.new(fn {[op, arg], idx} -> {idx, {op, String.to_integer(arg)}} end)
end
def run do
File.read!("input")
|> input_to_instrs()
|> find_corrupted()
|> IO.puts()
end
end
Day8Part2.run()
