Should groups have their scores for improving performance?

[exKAZUu]

Currently, groups do not have scores so score calculation frequently is required when sorting groups.
But, the number of problems is very few, so it does not affect performance, I think...

[ss0201]

Yeah, O(GPU) where G = # groups, P = # problems, U = # updates (F5) in delta t. A piece of cake, I think...