aoc2024/day-13/internal/one/solve.go

package one

import (
	"bytes"
	"math"

	log "github.com/sirupsen/logrus"

	"github.com/onyx-and-iris/aoc2024/day-13/internal/util"
)

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

	var total int
	for _, m := range machines {
		denominator := ((m.A.X * m.B.Y) - (m.B.X * m.A.Y))
		a_numerator := ((m.Prize.X * m.B.Y) - (m.Prize.Y * m.B.X))
		b_numerator := ((m.Prize.Y * m.A.X) - (m.Prize.X * m.A.Y))

		a := float64(a_numerator) / float64(denominator)
		b := float64(b_numerator) / float64(denominator)

		if a != math.Round(a) || b != math.Round(b) {
			continue
		}

		log.Debug(a, b)

		if a > 0 && b > 0 {
			total += 3*int(a) + int(b)
		}
	}

	return total, nil
}