Today, I was asked in an interview to build a data structure as follows:

Let there be some elements and some groups. Each element associated to 'exactly 1' group has a score. The data structure must support the following operations:

1. insert(el_id,grp_id,x): Insert element with id el_id with a score x to group with group_id grp_id
2. set(el_id,x): change the score of element with id el_id to x.
3. set(grp_id,x): change the score of all elements in the group with id grp_id to x.
4. print(grp_id): print the max score element's id in that group. (Return any if multiple exist)

Constraints:

1 <= no_of_elements <= 1e6
1 <= no_of_groups <= 5
1 <= score <= 5

I couldn't solve it during the interview and also couldn't think of any solution later. Would someone please help?