GFG Replace every element with the least greater element on its right

class Solution{
    public:
    vector<int> findLeastGreater(vector<int>& arr, int n) {
        vector<int> ans;
        set<int> s;
        
        for(int i=n-1;i>=0;i--)
        {
            auto it=s.upper_bound(arr[i]);
            if(it==s.end())
            {
                ans.push_back(-1);
            }
            else
            {
                ans.push_back(*it);
               
            }
            s.insert(arr[i]);
            
        }
        reverse(ans.begin(),ans.end());
        return ans;
        
    }
};