BFS in Sapper (code snippet)

// Breadth First Search

ArrayDeque<Pair<Int, Int>>().let { zeroes ->
    zeroes.addLast(xc to yc)

    val open = { xcc: Int, ycc: Int ->
        if (!(bts[xcc][ycc][1] as Boolean)) {
            (bts[xcc][ycc][0] as JButton).icon =
                ImageIcon(
                    getScaledImage(
                        ImageIO.read(
                            File("src/main/kotlin/utils/${numberTable[xcc][ycc]}.png")
                        ),
                        bt.width,
                        bt.height
                    )
                )

            bts[xcc][ycc][1] = true

            cellsLeft--

            if (numberTable[xcc][ycc] == 0)
                zeroes.addLast(xcc to ycc)
        }
    }

    while (zeroes.isNotEmpty()) {
        zeroes.first().let { (xc2, yc2) ->
            if (xc2 > 0)                    open(xc2 - 1, yc2)
            if (xc2 < x - 1)                open(xc2 + 1, yc2)
            if (yc2 > 0)                    open(xc2, yc2 - 1)
            if (yc2 < y - 1)                open(xc2, yc2 + 1)
            if (xc2 > 0 && yc2 > 0)         open(xc2 - 1, yc2 - 1)
            if (xc2 > 0 && yc2 < y - 1)     open(xc2 - 1, yc2 + 1)
            if (xc2 < x - 1 && yc2 > 0)     open(xc2 + 1, yc2 - 1)
            if (xc2 < x - 1 && yc2 < y - 1) open(xc2 + 1, yc2 + 1)
        }

        zeroes.removeFirst()
    }
}