2024 advent of code day 3

day_3.R

# first star
input <- paste0(readLines("input.txt"), collapse = " ") # ingest as one big blob
expression <- "mul\\([0-9]+,[0-9]+\\)"

# returns parsed string with generic function to allow for string to expression conversion
renamer <- function(x){
  str2lang(gsub("mul", "prod", regmatches(x, gregexpr(expression, x))))
}

multipliers <- renamer(input)
products <- sapply(multipliers, function(x) eval(parse(text = x)))
do.call(sum, products[-1])

# second star
enabled_input <- gsub("don't\\(\\).*?(?=do\\(\\))", "\\1", input, perl = TRUE)
enabled_multipliers <- renamer(enabled_input)
enabled_products <- sapply(enabled_multipliers, function(x) eval(parse(text = x)))
do.call(sum, enabled_products[-1])