51. N 皇后（算法200题-84）

var solveNQueens = function(n) {
    let list = [],
        temp = []
    backtrack(0, temp)
    return list
    // r === row || c == col || r - c === row -col || r + c === row + col
    function backtrack(row, temp) {
        if(row === n) {
            list.push(
                temp.map((c) => {
                    let arr = new Array(n).fill('.')
                    arr[c] = 'Q'
                    return arr.join('')
                })
            )
        }
        for(let col = 0; col < n; col++) {
            let canNotSet = temp.some((c, r) => {
                return c === col || (r-c) === (row - col) || (r + c) === (row + col)
            })
            if(canNotSet) continue
            backtrack(row + 1, [...temp, col])
        }
    }
};