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

package two

import (
	"bytes"

	log "github.com/sirupsen/logrus"
)

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

	const maxSeconds int = 10e3
	const width, height dimension = 101, 103

	var graph *graph
	var max, maxAtSecond int
	for i := 1; i <= maxSeconds; i++ {
		graph = newGraph(width, height)

		for _, robot := range robots {
			robot.update(width, height)
		}
		graph.update(robots)

		numNeighbours := evaluateNeighbours(graph, robots)
		if numNeighbours > max {
			max = numNeighbours
			maxAtSecond = i
		}
	}

	log.Debugf("\n%s\n", graph.String())

	return maxAtSecond, nil
}

func evaluateNeighbours(graph *graph, robots []*robot) int {
	var numNeighbours int
	for _, robot := range robots {
		for _, n := range neighbours(robot.position) {
			if graph.isOutOfBounds(n) {
				continue
			}

			if graph.valueAt(n) > 0 {
				numNeighbours++
			}
		}
	}
	return numNeighbours
}