135 lines
2.3 KiB
Go
135 lines
2.3 KiB
Go
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package main
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import (
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"errors"
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"fmt"
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"os"
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"strconv"
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"strings"
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)
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func noErr(err error) {
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if err != nil {
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panic(err)
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}
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}
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func main() {
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// parsing
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input, err := os.ReadFile("input.txt")
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noErr(err)
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lines := strings.Split(string(input), "\n")
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cards := make([]Card, len(lines))
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cardCounts := map[int]int{}
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for idx, l := range lines {
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card, err := LineToCard(l)
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noErr(err)
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cards[idx] = card
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cardCounts[card.Id] = 1
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}
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// part 1
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s := 0
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for _, c := range cards {
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s += c.Points()
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}
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println("Part 1:", s)
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// part 2
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t := 0
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for _, c := range cards {
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t += cardCounts[c.Id]
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for n := 1; n <= c.Wins(); n++ {
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_, exists := cardCounts[c.Id+n]
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if exists {
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cardCounts[c.Id+n] += cardCounts[c.Id]
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}
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}
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}
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println("Part 2:", t)
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}
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type Card struct {
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Id int
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WinningNs []int
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MyNs []int
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}
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func (card Card) Wins() int {
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c := 0
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for _, w := range card.WinningNs {
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for _, n := range card.MyNs {
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if w == n {
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c++
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}
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}
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}
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return c
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}
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func (card Card) Points() int {
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// math.Pow with into to float conversion feels wrong
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p := 1
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for _, w := range card.WinningNs {
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for _, n := range card.MyNs {
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if w == n {
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p *= 2
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}
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}
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}
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if p == 1 {
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return 0
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}
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return p / 2
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}
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var NoCutErr = errors.New("no cut found")
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func LineToCard(line string) (Card, error) {
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cardIdStr, nStr, f := strings.Cut(line, ":")
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if !f {
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return Card{}, fmt.Errorf("cut ':': %w", NoCutErr)
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}
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_, idStr, f := strings.Cut(cardIdStr, " ")
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if !f {
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return Card{}, fmt.Errorf("cut ' ': %w", NoCutErr)
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}
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id, err := strconv.Atoi(strings.TrimSpace(idStr))
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if err != nil {
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return Card{}, fmt.Errorf("card id: %w", err)
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}
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cardNStrs, myNStrs, f := strings.Cut(nStr, "|")
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if !f {
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return Card{}, fmt.Errorf("cut '|': %w", NoCutErr)
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}
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cardNs, err := strToNumbers(cardNStrs)
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if err != nil {
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return Card{}, fmt.Errorf("card ns: %w", err)
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}
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myNs, err := strToNumbers(myNStrs)
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if err != nil {
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return Card{}, fmt.Errorf("my ns: %w", err)
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}
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return Card{
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Id: id,
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WinningNs: cardNs,
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MyNs: myNs,
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}, nil
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}
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func strToNumbers(str string) ([]int, error) {
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nStrs := strings.Split(str, " ")
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ns := make([]int, 0)
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for _, nStr := range nStrs {
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if nStr == "" {
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continue
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}
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n, err := strconv.Atoi(strings.TrimSpace(nStr))
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if err != nil {
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return nil, err
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}
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ns = append(ns, n)
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}
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return ns, nil
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}
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