class Solution {public:    void swap(int &a, int &b)    {        int temp;        temp=a;        a=b;        b=temp;    }        void permutation(vector
     
      & nums, vector
      
       
        >& res, int n)    {        if(n==nums.size()-1)        {            res.push_back(nums);            return;        }        for(int i=n;i
        

> permute(vector

& nums) { vector

> res; if(nums.size()==0) return res; permutation(nums,res,0); return res; }};