aoc2024/day-17/internal/two/util.go

package two

import (
	"bufio"
	"io"
	"regexp"
	"strconv"
	"strings"
)

var (
	reRegister = regexp.MustCompile(`Register (?P<identifier>[A-Z]): (?P<value>[0-9]+)`)
	reProgram  = regexp.MustCompile(`Program: (?P<instructions>[0-9,]+)`)
)

func parseLines(r io.Reader) (map[string]int64, []int64, error) {
	registers := make(map[string]int64)
	var instructions []int64

	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := scanner.Text()

		switch line := line; {
		case reRegister.MatchString(line):
			m := reRegister.FindStringSubmatch(line)
			registers[m[1]] = mustConv(m[2])
		case reProgram.MatchString(line):
			m := reProgram.FindStringSubmatch(line)
			for _, n := range strings.Split(m[1], ",") {
				instructions = append(instructions, mustConv(n))
			}
		}
	}

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

	return registers, instructions, nil
}

func mustConv(s string) int64 {
	n, err := strconv.Atoi(s)
	if err != nil {
		panic(err)
	}
	return int64(n)
}