aoc2024/day-05/internal/one/solve.go

package one

import (
	"bytes"
	"slices"

	"github.com/onyx-and-iris/aoc2024/day-05/internal/util"
)

func Solve(buf []byte) (int, error) {
	r := bytes.NewReader(buf)
	updates, orderings, err := util.ParseLines(r)
	if err != nil {
		return 0, err
	}

	var sum int

	for _, update := range updates {
		beforeSort := slices.Clone(update.Pages)
		update.Sort(orderings)

		if slices.Compare(beforeSort, update.Pages) == 0 {
			sum += update.Pages[len(update.Pages)/2]
		}
	}

	return sum, nil
}