回溯
var permute = function(nums) {
if(nums.length===1)return [nums];
let arr = [];
function dfs(aim,nums){
if(nums.length===0){
arr.push(aim);
return;
}
for(let i=0;i<nums.length;i++){
let temp = [...nums];
let num = temp.splice(i,1);
dfs([...aim,num],temp);
}
}
dfs([],nums);
return arr;
};