Advent of Code 2023 Day 4

Day 4, thankfully, simplifies the input parsing. Each line of the input contains winning numbers and drawn numbers for a lottery game. Part 1 simply asks you to compute a score from the quantity
of winning numbers on each card:

Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11

Part 2 switches up the rules in an interesting way. Now, if card \(n\) has \(k\) winning numbers, you get copies of cards \(n+1\) through \(n+k\) inclusive. After simulating this process, you count the total number of cards. The difficulty comes from the fact that multiple copies of card \(n\) may exist. Since each card has an identical result, I can just multiply by the number of cards. The resulting loop runs quickly.

draw <- function(cards, won) {
    n <- length(cards)
    held <- rep(1, length.out = n)

    for (current in seq_len(n - 1)) {
        draws <- held[[current]]
        result <- won[[current]]
        if (result > 0) {
            received <- seq(current + 1, current + result, 1)
            # Clamp to number of cards
            received <- received[received <= n]
            held[received] <- held[received] + draws
        }
    }
    sum(held)
}