08: Matchsticks

library(mistlecode)
dt <- readLines("input.txt")

This doesn’t look too bad. Dealing with R’s \\ nonsense is going to be a pain.

Part 1

Getting the regex right was the worst part, just like I thought. \\ is the worst part about R.

literal_length <- 
  dt |>
  nchar() |>
  sum()

memory_length <-
  dt |>
  str_sub(start = 2) |>
  str_sub(end = -2) |>
  str_replace_all('\\\\x[0-9a-f]{2}', ' ') |>
  str_replace_all('\\\\\\"', ' ') |>
  str_replace_all('\\\\\\\\', ' ') |>
  nchar() |>
  sum()

literal_length - memory_length

[1] 1371

Part 2

Turns out R also auto-converts double spaces to tabs so to get two characters, you need three spaces…

total_length <-
  dt |>
  str_escape() |>
  str_replace_all('^"|"$', '   ') |>
  str_replace_all('\\\\x[0-9a-f]{2}', '    ') |>
  str_replace_all('\\\\\\"', '   ') |>
  str_replace_all('\\\\', ' ') |>
  nchar() |>
  sum()
total_length - literal_length

[1] 2117