2023 advent of code day 4

day_4.R

# first star
input <- read.table(file = "puzzle_input.txt", header = FALSE, sep = "\n")
matches <- mapply(function(x, y){sum(x%in%y)},
                  strsplit(gsub(".*:\\s+(.+)\\s+\\|.*", "\\1", input$V1),"\\s+"),
                  strsplit(gsub(".*\\|\\s+(.+)", "\\1", input$V1),  "\\s+"))

sum(sapply(matches[matches > 0], function(x){2^(x-1)}))

# second star
total_cards <- rep.int(1L, length(row(input))) # start cumulative total for each card

for (card in seq_along(total_cards[-1])) 
  {total_cards[card + seq_len(matches[card])] <- total_cards[card + seq_len(matches[card])] + total_cards[card]}
sum(total_cards)