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|
defmodule Day02 do
@add_opcode 1
@mul_opcode 2
@ret_opcode 99
@noun_address 1
@verb_address 2
@spec part1(binary) :: list
def part1(input), do: run(input, 12, 2)
@spec part2(binary) :: integer
def part2(input) do
for(
n <- 0..100,
v <- 0..100,
do: {n, v, run(input, n, v)}
)
|> Enum.find(&(elem(&1, 2) == 19_690_720))
|> then(fn {n, v, _} -> n * 100 + v end)
end
defp run(input, noun, verb) do
input
|> parse()
|> List.replace_at(@noun_address, noun)
|> List.replace_at(@verb_address, verb)
|> execute()
|> hd()
end
defp binary_op(program, op, a, b, out) do
program |> List.replace_at(out, op.(Enum.at(program, a), Enum.at(program, b)))
end
defp execute(program, pc \\ 0) do
instruction = program |> Enum.drop(pc) |> Enum.take(4)
case instruction do
[@add_opcode, a, b, out] ->
program
|> binary_op(&+/2, a, b, out)
|> execute(pc + 4)
[@mul_opcode, a, b, out] ->
program
|> binary_op(&*/2, a, b, out)
|> execute(pc + 4)
[@ret_opcode | _] ->
program
end
end
defp parse(input) do
input
|> String.split(",")
|> Enum.map(&Util.Integer.parse!/1)
end
end
input = Util.Input.read_text("day02")
input |> Day02.part1() |> IO.inspect()
input |> Day02.part2() |> IO.inspect()
|
