aoc2024/day-05/internal/util/util.go

package util

import (
	"bufio"
	"io"
	"strconv"
	"strings"

	"github.com/onyx-and-iris/aoc2024/day-05/internal/update"
)

func ParseLines(r io.Reader) ([]update.Update, map[int][]int, error) {
	var updates []update.Update
	orderings := make(map[int][]int, 0)

	var inUpdates bool
	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := scanner.Text()
		if len(line) == 0 {
			inUpdates = true
			continue
		}

		if inUpdates {
			var update update.Update
			for _, n := range strings.Split(line, ",") {
				update.Pages = append(update.Pages, mustConv(n))
			}
			updates = append(updates, update)
		} else {
			left, right := func() (int, int) {
				x := strings.Split(line, "|")
				return mustConv(x[0]), mustConv(x[1])
			}()
			orderings[left] = append(orderings[left], right)
		}
	}

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

	return updates, orderings, nil
}

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