aoc2024/day-03/internal/one/solve.go

package one

import (
	"bufio"
	"bytes"
	"io"
	"regexp"

	"github.com/onyx-and-iris/aoc2024/day-03/internal/util"
)

var reMul = regexp.MustCompile(`mul\(([0-9]{1,3}),([0-9]{1,3})\)`)

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

	return sum, nil
}

func parseLines(r io.Reader) (int, error) {
	var sum int

	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		matches := reMul.FindAllStringSubmatch(scanner.Text(), -1)
		for _, m := range matches {
			sum += util.MustConv(m[1]) * util.MustConv(m[2])
		}
	}

	if err := scanner.Err(); err != nil {
		return 0, err
	}

	return sum, nil
}