Gray Code gfg

class Solution
{
    public:

    vector<string> graycode(int n)
    {
        if(n==1)return {"0","1"};
        vector<string>prev=graycode(n-1);
        vector<string>main;
        for(int i=0;i<prev.size();i++){
            main.push_back("0"+prev[i]);
        }
        for(int i=prev.size()-1;i>=0;i--){
            main.push_back("1"+prev[i]);
        }
        return main;
    }
};