aoc2024/day-14/internal/two/util.go

package two

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

var reRobot = regexp.MustCompile(`p=(?P<px>\d+),(?P<py>\d+) v=(?P<vx>-?\d+),(?P<vy>-?\d+)`)

func parseLines(r io.Reader) ([]*robot, error) {
	var matches [][]string

	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := scanner.Text()
		m := reRobot.FindStringSubmatch(line)
		matches = append(matches, m)
	}

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

	var robots []*robot
	for _, m := range matches {
		robots = append(robots, newRobot(mustConv(m[1]), mustConv(m[2]), mustConv(m[3]), mustConv(m[4])))
	}

	return robots, nil
}

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

func replaceAtIndex(s string, r rune, i int) string {
	out := []rune(s)
	out[i] = r
	return string(out)
}