03: Mull It Over

library(mistlecode)

options(scipen = 999)

dt <- readLines("input.txt")

Part 1

I’m really pleased with this. Doing the parse() |> eval() is super super dangerous and should never be done, but it works so I’m happy. I got 343 on the leaderboard which is my best ever.

mul <- function(x, y) x * y
dt |>
  stringr::str_extract_all('mul\\(\\d+,\\d+\\)') |>
  unlist() |>
  purrr::map_int(\(x) {
    x |>
      parse(text = _) |>
      eval()
  }) |>
  sum()

[1] 170068701

Part 2

I didn’t realize the example input changed which messed me up a bit. Then I just had to get my regex right and I was good to go. I’m also pleased with my little if...else if chain. I got an error when x was a mul() call, but then realized that I didn’t have to explicitly check because I was already checking for do() and don't() and if it’s not either of those, then it must be a mul(). Oh, and 502 on the leaderboard for part 2 would’ve been a best ever if not for part 1!

do <- TRUE
dt |>
  stringr::str_extract_all("mul\\(\\d+,\\d+\\)|do\\(\\)|don't\\(\\)") |>
  unlist() |>
  purrr::map_int(\(x) {
    if (x == "don't()") do <<- FALSE 
    else if (x == "do()") do <<- TRUE 
    else if (do) {
      x <-
        x |>
        parse(text = _) |>
        eval()
      return(x)
    }
    return(0)
  }) |>
  sum()

[1] 78683433