Leecode 46. 全排列

var permute = function(nums) {
    var res = []
    function backtrack(path){
        if(path.length==nums.length){
            res.push(path)
            return
        }
        nums.forEach(n=>{
            if(path.includes(n)){return}
            backtrack(path.concat(n))
        })
    }
    backtrack([])
    return res
};