adventoc/2024/day03.go

package adventoc2024

import (
	"io"
	"regexp"
	"strings"
)

type Day3 struct{}

func (d Day3) Part1(r io.Reader) string {
	var bd strings.Builder
	var sum int
	io.Copy(&bd, r)

	re := regexp.MustCompile(`mul\((\d{1,3}),(\d{1,3})\)`)

	matches := re.FindAllStringSubmatch(bd.String(), -1)

	for _, match := range matches {
		sum += atoi(match[1]) * atoi(match[2])
	}
	return printi(sum)
}

func (d Day3) Part2(r io.Reader) string {
	var bd strings.Builder
	var sum int
	io.Copy(&bd, r)

	re := regexp.MustCompile(`mul\((\d{1,3}),(\d{1,3})\)|do\(\)|don\'t\(\)`)

	matches := re.FindAllStringSubmatch(bd.String(), -1)

	var skip bool
	for _, match := range matches {
		switch match[0] {
		case "do()":
			skip = false
		case "don't()":
			skip = true
		default:
			if !skip {
				sum += atoi(match[1]) * atoi(match[2])
			}
		}
	}
	return printi(sum)
}