52

在n皇后的问题上稍做修改，faster than 89%

/**
 * @param {number} n
 * @return {number}
 */
var totalNQueens = function(n) {
    var pos = []
    var res = []
    totalNQueen(n, 0, pos, res)
    return res.length
};
var totalNQueen = function(n, cur, pos, res){
    if(cur === n) res.push(1)
    for(var i = 0; i < n; i++){
        pos[cur] = i
        if(isValid(n, cur, i, pos)) totalNQueen(n, cur + 1, pos, res)
    }
}
var isValid = function(n, cur, index, pos){
    for(var i = cur - 1, j = 1; i >= 0; i--, j++){
        if(pos[i] === index || pos[i] === index + j || pos[i] === index - j) return false
    }
    return true
}