如何找到集合的交集

Question

I have N number of sets of let us say integers. Now I want a function, which finds me the intersection of those sets. For example, for the following

Set1 = { A, D, E, F, G, L }
Set2 = { N, K, E, G, B, C }
Set3 = { K, P, Q, E, F, G }
Set4 = { Z, Y, C, G, F, E }

Since E and G is in every set, I should get { E, G } as output. What is the easiest way to do this. I know it is not very difficult to write your own code to do this, but perhaps there is already an STL or any other library function to this, in which I'm interested.

Answer 1

Two possible solutions I can think of

1. Store your sets in vectors. Sort the vectors using std::sort , and compute set intersection using std::set_intersection
2. Store your sets in std::set , which causes the elements to be sorted anyway, and use std::set_intersection

Answer 2

See std::set_intersection . (As pointed out already in the comments, you probably want intersection, not union.)