Bitwise magic 8 queen problem resolver

8 queen problem.js

/**
 * @param {number} n
 * @return {number}
 */
var totalNQueens = function(n) {
    var width = n
    var total = 0

    function run(x, ltu, ltr, ltd) {
        if (x >= width) {
            total++
            return
        }

        for (let i = 0; i < width; i++) {
            const ltuMask = 1 << (x + i)
            const ltrMask = 1 << i
            const ltdMask = 1 << (x - i + width)

            if (
                (ltu & ltuMask) ||
                (ltr & ltrMask) ||
                (ltd & ltdMask)
            ) {
                continue
            }

            run(
                x + 1,
                ltu | ltuMask,
                ltr | ltrMask,
                ltd | ltdMask
            )
        }
    }

    run(0, 0, 0, 0)
    return total
};