2025 advent of code day 2

day_2.R

input <- sapply(read.csv("input.txt", header = FALSE), strsplit, "-")
input <- lapply(input, function(x){as.character(x[1]:x[2])})

get_invalids <- function(x, new = FALSE){
  ranges <- sapply(x, function(x){subset(x, nchar(x) %% 2  == 0)}) # repeating numbers are of even length
  invalids <- sapply(ranges, function(x) {as.numeric(grep("^(\\d+)\\1$", x, value = TRUE))})
  if (new == TRUE){
    invalids <- sapply(x, function(i) {as.numeric(grep("^(\\d+)(\\1)+$", i, value = TRUE))})
  }
  return(invalids)
}

invalids <- lapply(sapply(input, get_invalids), unlist)
do.call(sum, invalids)

# second star
new_invalids <- lapply(sapply(input, function (x) {get_invalids(x, new = TRUE)}), unlist)              
do.call(sum, new_invalids)