advent-of-code/aoc2023/day04/main.go
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2024-10-26 11:38:44 -06:00

101 lines
2.1 KiB
Go

package main
import (
"bufio"
_ "embed"
"log/slog"
"strconv"
"strings"
aoc "go.sour.is/advent-of-code"
)
//go:embed input.txt
var input []byte
type card struct {
card int
winner []int
scratch []int
copies int
}
func main() { aoc.MustResult(aoc.Runner(run)) }
type result struct {
points int
cards int
}
func run(scan *bufio.Scanner) (result, error) {
cards := []*card{}
for scan.Scan() {
pfx, text, ok := strings.Cut(scan.Text(), ":")
if !ok || !strings.HasPrefix(pfx, "Card ") {
continue
}
num := aoc.Atoi(strings.TrimSpace(strings.SplitN(pfx, " ", 2)[1]))
cards = append(cards, &card{card: num})
buf := make([]rune, 0, 4)
winner := true
for _, a := range text {
if a >= '0' && a <= '9' {
buf = append(buf, a)
continue
}
if a == ' ' && len(buf) > 0 {
num, _ = strconv.Atoi(string(buf))
buf = buf[:0]
if winner {
cards[len(cards)-1].winner = append(cards[len(cards)-1].winner, num)
} else {
cards[len(cards)-1].scratch = append(cards[len(cards)-1].scratch, num)
}
}
if a == '|' {
winner = false
}
}
if len(buf) > 0 {
num = aoc.Atoi(string(buf))
buf = buf[:0]
_ = buf // ignore
cards[len(cards)-1].scratch = append(cards[len(cards)-1].scratch, num)
}
}
var sumPoints int
var sumCards int
for _, card := range cards {
m := []int{}
for _, w := range card.winner {
for _, s := range card.scratch {
if w == s {
m = append(m, w)
}
}
}
if len(m) > 0 {
sumPoints += 1 << (len(m) - 1)
for i, c := range cards[card.card:min(card.card+len(m), len(cards))] {
c.copies += 1 + 1*card.copies
slog.Debug("cards", "card", card.card, "wins", i+1, "with", card.copies, "copies, wins", len(m), "giving", 1+1*card.copies, "for card", c.card, "total", c.copies)
}
}
sumCards += 1 + 1*card.copies
slog.Debug("cards", "card", card.card, "wins", len(m), "as", 1, "+", 1*card.copies, "for", 1+1*card.copies, "copies. total", sumCards)
slog.Debug("points", "card", card.card, "match", m, "score", sumPoints)
}
return result{sumPoints, sumCards}, nil
}