package q1926

const (
	EMPTY byte = '.'
	WALL  byte = '+'
)

func nearestExit(maze [][]byte, entrance []int) int {
	queue := make([][3]int, 0, len(maze)) // row, col, step
	queue = append(queue, [3]int{entrance[0], entrance[1], 0})
	maze[entrance[0]][entrance[1]] = WALL // mark as visited

	var add = func(r, c, s int) bool {
		if r < 0 || c < 0 || r >= len(maze) || c >= len(maze[0]) || maze[r][c] != EMPTY {
			return false
		}

		if r == 0 || c == 0 || r == len(maze)-1 || c == len(maze[0])-1 {
			return true // found
		}

		maze[r][c] = WALL
		queue = append(queue, [3]int{r, c, s})
		return false
	}

	for ; len(queue) > 0; queue = queue[1:] {
		cur := queue[0]
		r, c, s := cur[0], cur[1], cur[2]
		if add(r, c+1, s+1) ||
			add(r, c-1, s+1) ||
			add(r+1, c, s+1) ||
			add(r-1, c, s+1) {
			return s + 1
		}
	}
	return -1
}

var _ = nearestExit