aoc2024/day-04/internal/one/solve.go

package one

import (
	"bytes"

	log "github.com/sirupsen/logrus"
)

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

	var sum int

	for i := 0; i < len(graph.data); i++ {
		for j := 0; j < len(graph.data[i]); j++ {
			current := newPoint(j, i)
			if graph.valueAt(current) == 'X' {
				for _, n := range neighbours(current) {
					if graph.isOutOfBounds(n) {
						continue
					}

					if checkNeighbours(graph, n, "MAS") {
						sum++
					}
				}
			}
		}
	}

	return sum, nil
}

func checkNeighbours(graph *graph, n point, word string) bool {
	if len(word) == 0 {
		log.Debug("we found a full XMAS")
		return true
	}

	if graph.isOutOfBounds(n) {
		return false
	}

	if graph.valueAt(n) != rune(word[0]) {
		return false
	}

	return checkNeighbours(graph, neighbours(n)[n.direction], word[1:])
}