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

package two

import (
	"bytes"
	"slices"

	"github.com/onyx-and-iris/aoc2024/day-04/internal/util"
)

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

	var sum int

	for i := 0; i < len(lines); i++ {
		for j := 0; j < len(lines[i]); j++ {
			if lines[i][j] == 'A' {
				neighbours := newNeighbours(j, i)
				if func() bool {
					for _, n := range neighbours.all() {
						if n.outOfBounds(lines) {
							return true
						}
						if !slices.Contains([]rune{'M', 'S'}, n.value(lines)) {
							return true
						}
					}
					return false
				}() {
					continue
				}

				matrix := newMatrix(
					rune(lines[i][j]),
					neighbours.NW.value(lines),
					neighbours.NE.value(lines),
					neighbours.SE.value(lines),
					neighbours.SW.value(lines),
				)

				if matrix.validate() {
					sum++
				}
			}
		}
	}

	return sum, nil
}