aoc2024/day-06/internal/one/solve.go

package one

import (
	"bytes"

	log "github.com/sirupsen/logrus"
)

var Visited = make(map[coords]struct{})

func Solve(buf []byte) (int, error) {
	r := bytes.NewReader(buf)
	graph, err := parseLines(r)
	if err != nil {
		return 0, err
	}
	log.Debug(graph.startPoint.String())

	var count int
	count = nextStep(graph.startPoint, graph, Visited, count)
	log.Debugf("path walked: \n%s\n", graph.debug(Visited))

	return count, nil
}

func nextStep(point point, graph *graph, visited map[coords]struct{}, count int) int {
	_, ok := visited[point.coords]
	if !ok {
		visited[point.coords] = struct{}{}
		count++
	}

	log.Debugf("count: %d\n", count)

	if point.X == 0 && point.direction == W ||
		point.Y == 0 && point.direction == N ||
		point.Y == len(graph.data)-1 && point.direction == S ||
		point.X == len(graph.data[point.Y])-1 && point.direction == E {
		return count
	}

	next := nextPoint(point)
	log.Debug(next.String())
	log.Debug(string(graph.data[next.Y][next.X]))
	if graph.data[next.Y][next.X] == '#' {
		next.recalibrate()
		log.Debugf("switched direction to %d", next.direction)
	}

	return nextStep(next, graph, visited, count)
}