aoc2023/day-4/two.go

package main

// Cards represents a single card.
// it tracks its matching numbers and occurrences
type Card struct {
	matches     int
	occurrences int
}

var cards = []Card{}

// two returns the total number of occurrences for all cards
func two(lines []string) (int, error) {
	var sum = 0

	for i := range cards {
		cards[i].occurrences++

		for j := i + 1; j <= i+cards[i].matches; j++ {
			cards[j].occurrences += cards[i].occurrences
		}

		sum += cards[i].occurrences
	}

	return sum, nil
}