11239 - Open Source - UVA

Data Structures - STL map or set - sorting

As shown in the problem description, you have to count the number of students who have signed up for each project. There are some important hints in this problem that you have to concern :
If someone has signed up for more than one project do not count him for any of them.
If someone has written his name for a project more than one time, It's OK, just count him once in that project.

Data structure I use in this problem :
map (string, set(string) ) === to save for each project which students want to attend
map (string, string) === to save this student is singed for which project previously
set (string) === to save which student has signed up and can not attend any other project, if a student want to sign up for more than one project I find the previous project he/she has signed up for and delete him/her from that list
vector (int, string) === to produce output and sort it by number of students attending each project and then alphabetically by the name of the project