permutations

class Solution {
public:
    vector<vector<int> > permute(vector<int> &num) {
        permutation(num,0);
        return ans;
    }
    void permutation(vector<int>&num,int index){
        if(index==num.size()-1){
            ans.push_back(num);
            return;
        }
        for(int i=index;i<num.size();i++)
        {
            swap(num[index],num[i]);
            permutation(num,index+1);
            swap(num[index],num[i]);
        }
    }
private:
    vector<vector<int>>ans;
};