Permutations

class Solution {
public:
    void swap(int &a, int &b)
    {
        int temp;
        temp=a;
        a=b;
        b=temp;
    }
    
    void permutation(vector<int>& nums, vector<vector<int>>& res, int n)
    {
        if(n==nums.size()-1)
        {
            res.push_back(nums);
            return;
        }
        for(int i=n;i<nums.size();i++)
        {
            swap(nums[i],nums[n]);
            permutation(nums,res,n+1);
            swap(nums[i],nums[n]);
        }
        
    }
    
    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int>> res;
        if(nums.size()==0)
            return res;
        permutation(nums,res,0);
        return res;
    }
};