aoc2024/day-08/internal/two/util.go

package two

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

var reMatchAntennae = regexp.MustCompile(`[a-zA-Z0-9]`)

func parseLines(r io.Reader) (*graph, error) {
	graph := newGraph()

	var linecount int
	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := scanner.Text()
		graph.data = append(graph.data, line)

		for _, m := range reMatchAntennae.FindAllStringIndex(line, -1) {
			graph.antennae = append(
				graph.antennae,
				newAntenna(m[0], linecount, rune(line[m[0]])),
			)
		}
		linecount++
	}

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

	return graph, nil
}

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